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	$132.28	7.302%	$141.9391	$141.94	$141.95	$141.90
Purchase #2	$197.61	12.615%	$222.5385	$222.54	$222.55	$222.50
Purchase #3	$62.63	12.580%	$70.5089	$70.51	$70.50	$70.50
Purchase #4	$86.80	4.438%	$90.6522	$90.65	$90.65	$90.70
Purchase #5	$146.51	13.264%	$165.9431	$165.94	$165.95	$165.90
Purchase #6	$188.51	5.354%	$198.6028	$198.60	$198.60	$198.60
Purchase #7	$47.72	11.778%	$53.3405	$53.34	$53.35	$53.30
7 purchase totals =	$862.06		$943.5251	$943.52	$943.55	$943.40