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	$116.70	9.523%	$127.8133	$127.81	$127.80	$127.80
Purchase #2	$55.55	11.497%	$61.9366	$61.94	$61.95	$61.90
Purchase #3	$8.39	9.781%	$9.2106	$9.21	$9.20	$9.20
Purchase #4	$247.33	7.103%	$264.8978	$264.90	$264.90	$264.90
Purchase #5	$237.76	7.302%	$255.1212	$255.12	$255.10	$255.10
Purchase #6	$83.67	8.401%	$90.6991	$90.70	$90.70	$90.70
Purchase #7	$78.82	7.863%	$85.0176	$85.02	$85.00	$85.00
7 purchase totals =	$828.22		$894.6962	$894.70	$894.65	$894.60