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	$76.28	9.672%	$83.6578	$83.66	$83.65	$83.70
Purchase #2	$79.67	11.559%	$88.8791	$88.88	$88.90	$88.90
Purchase #3	$78.98	12.487%	$88.8422	$88.84	$88.85	$88.80
Purchase #4	$242.78	5.258%	$255.5454	$255.55	$255.55	$255.50
Purchase #5	$244.91	7.754%	$263.9003	$263.90	$263.90	$263.90
Purchase #6	$173.35	5.388%	$182.6901	$182.69	$182.70	$182.70
Purchase #7	$123.52	6.777%	$131.891	$131.89	$131.90	$131.90
7 purchase totals =	$1,019.49		$1,095.4059	$1,095.41	$1,095.45	$1,095.40