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	$216.29	3.333%	$223.4989	$223.50	$223.50	$223.50
Purchase #2	$147.99	4.538%	$154.7058	$154.71	$154.70	$154.70
Purchase #3	$146.81	3.553%	$152.0262	$152.03	$152.05	$152.00
Purchase #4	$128.72	10.667%	$142.4506	$142.45	$142.45	$142.50
Purchase #5	$159.73	5.145%	$167.9481	$167.95	$167.95	$167.90
Purchase #6	$178.44	13.872%	$203.1932	$203.19	$203.20	$203.20
Purchase #7	$111.79	10.651%	$123.6968	$123.70	$123.70	$123.70
7 purchase totals =	$1,089.77		$1,167.5196	$1,167.53	$1,167.55	$1,167.50