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	$141.48	4.315%	$147.5849	$147.58	$147.60	$147.60
Purchase #2	$237.25	7.681%	$255.4732	$255.47	$255.45	$255.50
Purchase #3	$59.59	8.632%	$64.7338	$64.73	$64.75	$64.70
Purchase #4	$230.58	7.448%	$247.7536	$247.75	$247.75	$247.80
Purchase #5	$196.98	12.738%	$222.0713	$222.07	$222.05	$222.10
Purchase #6	$165.75	11.137%	$184.2096	$184.21	$184.20	$184.20
Purchase #7	$85.71	5.195%	$90.1626	$90.16	$90.15	$90.20
7 purchase totals =	$1,117.34		$1,211.9890	$1,211.97	$1,211.95	$1,212.10