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	$147.71	8.542%	$160.3274	$160.33	$160.35	$160.30
Purchase #2	$215.70	4.388%	$225.1649	$225.16	$225.15	$225.20
Purchase #3	$205.53	13.111%	$232.477	$232.48	$232.50	$232.50
Purchase #4	$86.46	8.443%	$93.7598	$93.76	$93.75	$93.80
Purchase #5	$53.71	10.359%	$59.2738	$59.27	$59.25	$59.30
Purchase #6	$25.46	11.825%	$28.4706	$28.47	$28.45	$28.50
Purchase #7	$134.37	9.347%	$146.9296	$146.93	$146.95	$146.90
7 purchase totals =	$868.94		$946.4031	$946.40	$946.40	$946.50