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	$130.77	13.346%	$148.2226	$148.22	$148.20	$148.20
Purchase #2	$55.69	5.132%	$58.548	$58.55	$58.55	$58.50
Purchase #3	$77.54	6.446%	$82.5382	$82.54	$82.55	$82.50
Purchase #4	$11.60	6.778%	$12.3862	$12.39	$12.40	$12.40
Purchase #5	$84.38	6.533%	$89.8925	$89.89	$89.90	$89.90
Purchase #6	$178.58	10.739%	$197.7577	$197.76	$197.75	$197.80
Purchase #7	$187.76	8.395%	$203.5225	$203.52	$203.50	$203.50
7 purchase totals =	$726.32		$792.8677	$792.87	$792.85	$792.80