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	$88.70	4.674%	$92.8458	$92.85	$92.85	$92.80
Purchase #2	$83.76	7.843%	$90.3293	$90.33	$90.35	$90.30
Purchase #3	$37.84	11.772%	$42.2945	$42.29	$42.30	$42.30
Purchase #4	$24.77	7.853%	$26.7152	$26.72	$26.70	$26.70
Purchase #5	$92.37	8.237%	$99.9785	$99.98	$100.00	$100.00
Purchase #6	$179.86	13.712%	$204.5224	$204.52	$204.50	$204.50
Purchase #7	$22.72	11.240%	$25.2737	$25.27	$25.25	$25.30
7 purchase totals =	$530.02		$581.9594	$581.96	$581.95	$581.90