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	$155.31	13.173%	$175.769	$175.77	$175.75	$175.80
Purchase #2	$172.89	11.171%	$192.2035	$192.20	$192.20	$192.20
Purchase #3	$203.33	13.468%	$230.7145	$230.71	$230.70	$230.70
Purchase #4	$246.70	9.258%	$269.5395	$269.54	$269.55	$269.50
Purchase #5	$116.90	11.376%	$130.1985	$130.20	$130.20	$130.20
Purchase #6	$33.43	12.688%	$37.6716	$37.67	$37.65	$37.70
Purchase #7	$23.59	5.716%	$24.9384	$24.94	$24.95	$24.90
7 purchase totals =	$952.15		$1,061.0350	$1,061.03	$1,061.00	$1,061.00