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	$49.74	7.575%	$53.5078	$53.51	$53.50	$53.50
Purchase #2	$86.86	4.173%	$90.4847	$90.48	$90.50	$90.50
Purchase #3	$221.56	12.472%	$249.193	$249.19	$249.20	$249.20
Purchase #4	$227.92	12.558%	$256.5422	$256.54	$256.55	$256.50
Purchase #5	$150.28	3.155%	$155.0213	$155.02	$155.00	$155.00
Purchase #6	$85.73	4.594%	$89.6684	$89.67	$89.65	$89.70
Purchase #7	$83.77	8.659%	$91.0236	$91.02	$91.00	$91.00
7 purchase totals =	$905.86		$985.4410	$985.43	$985.40	$985.40