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	$163.73	12.684%	$184.4975	$184.50	$184.50	$184.50
Purchase #2	$210.57	5.659%	$222.4862	$222.49	$222.50	$222.50
Purchase #3	$77.31	5.494%	$81.5574	$81.56	$81.55	$81.60
Purchase #4	$240.33	6.456%	$255.8457	$255.85	$255.85	$255.80
Purchase #5	$178.86	9.275%	$195.4493	$195.45	$195.45	$195.40
Purchase #6	$64.64	9.290%	$70.6451	$70.65	$70.65	$70.60
Purchase #7	$136.71	9.319%	$149.45	$149.45	$149.45	$149.50
7 purchase totals =	$1,072.15		$1,159.9312	$1,159.95	$1,159.95	$1,159.90