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	$29.44	9.534%	$32.2468	$32.25	$32.25	$32.20
Purchase #2	$246.40	10.433%	$272.1069	$272.11	$272.10	$272.10
Purchase #3	$53.78	8.868%	$58.5492	$58.55	$58.55	$58.50
Purchase #4	$127.34	11.244%	$141.6581	$141.66	$141.65	$141.70
Purchase #5	$34.79	5.856%	$36.8273	$36.83	$36.85	$36.80
Purchase #6	$66.91	4.762%	$70.0963	$70.10	$70.10	$70.10
Purchase #7	$60.85	11.570%	$67.8903	$67.89	$67.90	$67.90
7 purchase totals =	$619.51		$679.3749	$679.39	$679.40	$679.30