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	$68.71	6.188%	$72.9618	$72.96	$72.95	$73.00
Purchase #2	$213.31	10.740%	$236.2195	$236.22	$236.20	$236.20
Purchase #3	$145.78	5.270%	$153.4626	$153.46	$153.45	$153.50
Purchase #4	$218.26	4.607%	$228.3152	$228.32	$228.30	$228.30
Purchase #5	$91.97	5.855%	$97.3548	$97.35	$97.35	$97.40
Purchase #6	$39.62	8.201%	$42.8692	$42.87	$42.85	$42.90
Purchase #7	$155.90	10.630%	$172.4722	$172.47	$172.45	$172.50
7 purchase totals =	$933.55		$1,003.6553	$1,003.65	$1,003.55	$1,003.80