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	$39.39	10.703%	$43.6059	$43.61	$43.60	$43.60
Purchase #2	$111.41	12.672%	$125.5279	$125.53	$125.55	$125.50
Purchase #3	$163.80	13.388%	$185.7295	$185.73	$185.75	$185.70
Purchase #4	$26.37	10.565%	$29.156	$29.16	$29.15	$29.20
Purchase #5	$207.71	12.440%	$233.5491	$233.55	$233.55	$233.50
Purchase #6	$60.56	11.193%	$67.3385	$67.34	$67.35	$67.30
Purchase #7	$37.73	10.406%	$41.6562	$41.66	$41.65	$41.70
7 purchase totals =	$646.97		$726.5631	$726.58	$726.60	$726.50