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	$47.41	5.773%	$50.147	$50.15	$50.15	$50.10
Purchase #2	$221.71	10.695%	$245.4219	$245.42	$245.40	$245.40
Purchase #3	$229.65	10.341%	$253.3981	$253.40	$253.40	$253.40
Purchase #4	$62.67	13.511%	$71.1373	$71.14	$71.15	$71.10
Purchase #5	$152.98	5.659%	$161.6371	$161.64	$161.65	$161.60
Purchase #6	$67.33	5.662%	$71.1422	$71.14	$71.15	$71.10
Purchase #7	$123.43	5.812%	$130.6038	$130.60	$130.60	$130.60
7 purchase totals =	$905.18		$983.4874	$983.49	$983.50	$983.30