Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$156.46	10.494%	$172.8789	$172.88	$172.90	$172.90
Purchase #2	$182.79	9.676%	$200.4768	$200.48	$200.50	$200.50
Purchase #3	$87.53	7.721%	$94.2882	$94.29	$94.30	$94.30
Purchase #4	$141.95	9.611%	$155.5928	$155.59	$155.60	$155.60
Purchase #5	$156.71	8.649%	$170.2638	$170.26	$170.25	$170.30
Purchase #6	$207.35	7.172%	$222.2211	$222.22	$222.20	$222.20
Purchase #7	$178.62	6.104%	$189.523	$189.52	$189.50	$189.50
7 purchase totals =	$1,111.41		$1,205.2446	$1,205.24	$1,205.25	$1,205.30