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	$111.92	9.456%	$122.5032	$122.50	$122.50	$122.50
Purchase #2	$238.40	7.530%	$256.3515	$256.35	$256.35	$256.40
Purchase #3	$176.77	11.396%	$196.9147	$196.91	$196.90	$196.90
Purchase #4	$188.96	3.495%	$195.5642	$195.56	$195.55	$195.60
Purchase #5	$47.30	10.850%	$52.4321	$52.43	$52.45	$52.40
Purchase #6	$115.28	13.571%	$130.9246	$130.92	$130.90	$130.90
Purchase #7	$5.35	10.590%	$5.9166	$5.92	$5.90	$5.90
7 purchase totals =	$883.98		$960.6069	$960.59	$960.55	$960.60