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	$212.34	13.151%	$240.2648	$240.26	$240.25	$240.30
Purchase #2	$179.30	9.707%	$196.7047	$196.70	$196.70	$196.70
Purchase #3	$70.59	11.480%	$78.6937	$78.69	$78.70	$78.70
Purchase #4	$155.54	11.145%	$172.8749	$172.87	$172.85	$172.90
Purchase #5	$212.59	8.352%	$230.3455	$230.35	$230.35	$230.30
Purchase #6	$149.91	10.534%	$165.7015	$165.70	$165.70	$165.70
Purchase #7	$55.53	3.329%	$57.3786	$57.38	$57.40	$57.40
7 purchase totals =	$1,035.80		$1,141.9637	$1,141.95	$1,141.95	$1,142.00