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	$47.69	12.161%	$53.4896	$53.49	$53.50	$53.50
Purchase #2	$61.52	12.531%	$69.2291	$69.23	$69.25	$69.20
Purchase #3	$95.95	9.585%	$105.1468	$105.15	$105.15	$105.10
Purchase #4	$99.47	11.277%	$110.6872	$110.69	$110.70	$110.70
Purchase #5	$27.85	13.393%	$31.58	$31.58	$31.60	$31.60
Purchase #6	$151.63	3.493%	$156.9264	$156.93	$156.95	$156.90
Purchase #7	$192.33	4.306%	$200.6117	$200.61	$200.60	$200.60
7 purchase totals =	$676.44		$727.6708	$727.68	$727.75	$727.60