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	$55.58	11.394%	$61.9128	$61.91	$61.90	$61.90
Purchase #2	$213.39	8.555%	$231.6455	$231.65	$231.65	$231.60
Purchase #3	$89.83	5.266%	$94.5604	$94.56	$94.55	$94.60
Purchase #4	$226.65	8.146%	$245.1129	$245.11	$245.10	$245.10
Purchase #5	$94.71	6.291%	$100.6682	$100.67	$100.65	$100.70
Purchase #6	$119.88	8.518%	$130.0914	$130.09	$130.10	$130.10
Purchase #7	$116.54	5.643%	$123.1164	$123.12	$123.10	$123.10
7 purchase totals =	$916.58		$987.1076	$987.11	$987.05	$987.10