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	$49.63	10.195%	$54.6898	$54.69	$54.70	$54.70
Purchase #2	$40.70	4.847%	$42.6727	$42.67	$42.65	$42.70
Purchase #3	$45.27	11.582%	$50.5132	$50.51	$50.50	$50.50
Purchase #4	$158.73	8.644%	$172.4506	$172.45	$172.45	$172.50
Purchase #5	$31.89	12.496%	$35.875	$35.88	$35.90	$35.90
Purchase #6	$68.63	5.644%	$72.5035	$72.50	$72.50	$72.50
Purchase #7	$131.34	9.499%	$143.816	$143.82	$143.80	$143.80
7 purchase totals =	$526.19		$572.5208	$572.52	$572.50	$572.60