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	$102.90	12.872%	$116.1453	$116.15	$116.15	$116.10
Purchase #2	$149.86	3.248%	$154.7275	$154.73	$154.75	$154.70
Purchase #3	$26.31	3.489%	$27.228	$27.23	$27.25	$27.20
Purchase #4	$69.74	12.497%	$78.4554	$78.46	$78.45	$78.50
Purchase #5	$50.72	7.252%	$54.3982	$54.40	$54.40	$54.40
Purchase #6	$132.88	11.148%	$147.6935	$147.69	$147.70	$147.70
Purchase #7	$152.74	4.616%	$159.7905	$159.79	$159.80	$159.80
7 purchase totals =	$685.15		$738.4384	$738.45	$738.50	$738.40