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	$48.77	9.343%	$53.3266	$53.33	$53.35	$53.30
Purchase #2	$185.59	3.570%	$192.2156	$192.22	$192.20	$192.20
Purchase #3	$203.43	13.231%	$230.3458	$230.35	$230.35	$230.30
Purchase #4	$200.89	4.206%	$209.3394	$209.34	$209.35	$209.30
Purchase #5	$20.50	6.148%	$21.7603	$21.76	$21.75	$21.80
Purchase #6	$54.71	9.121%	$59.7001	$59.70	$59.70	$59.70
Purchase #7	$30.62	12.667%	$34.4986	$34.50	$34.50	$34.50
7 purchase totals =	$744.51		$801.1864	$801.20	$801.20	$801.10