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	$81.32	13.325%	$92.1559	$92.16	$92.15	$92.20
Purchase #2	$207.57	4.390%	$216.6823	$216.68	$216.70	$216.70
Purchase #3	$178.60	5.589%	$188.582	$188.58	$188.60	$188.60
Purchase #4	$204.32	9.489%	$223.7079	$223.71	$223.70	$223.70
Purchase #5	$235.75	7.808%	$254.1574	$254.16	$254.15	$254.20
Purchase #6	$185.43	5.780%	$196.1479	$196.15	$196.15	$196.10
Purchase #7	$231.72	11.240%	$257.7653	$257.77	$257.75	$257.80
7 purchase totals =	$1,324.71		$1,429.1987	$1,429.21	$1,429.20	$1,429.30