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	$146.51	12.280%	$164.5014	$164.50	$164.50	$164.50
Purchase #2	$104.69	4.603%	$109.5089	$109.51	$109.50	$109.50
Purchase #3	$189.79	6.680%	$202.468	$202.47	$202.45	$202.50
Purchase #4	$170.72	9.335%	$186.6567	$186.66	$186.65	$186.70
Purchase #5	$228.82	9.155%	$249.7685	$249.77	$249.75	$249.80
Purchase #6	$65.91	8.204%	$71.3173	$71.32	$71.30	$71.30
Purchase #7	$45.45	4.382%	$47.4416	$47.44	$47.45	$47.40
7 purchase totals =	$951.89		$1,031.6624	$1,031.67	$1,031.60	$1,031.70