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	$213.81	12.689%	$240.9404	$240.94	$240.95	$240.90
Purchase #2	$178.32	9.432%	$195.1391	$195.14	$195.15	$195.10
Purchase #3	$48.70	3.736%	$50.5194	$50.52	$50.50	$50.50
Purchase #4	$12.32	12.761%	$13.8922	$13.89	$13.90	$13.90
Purchase #5	$40.76	10.190%	$44.9134	$44.91	$44.90	$44.90
Purchase #6	$18.90	8.114%	$20.4335	$20.43	$20.45	$20.40
Purchase #7	$225.44	4.462%	$235.4991	$235.50	$235.50	$235.50
7 purchase totals =	$738.25		$801.3371	$801.33	$801.35	$801.20