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	$211.71	10.758%	$234.4858	$234.49	$234.50	$234.50
Purchase #2	$133.72	3.485%	$138.3801	$138.38	$138.40	$138.40
Purchase #3	$63.94	13.113%	$72.3245	$72.32	$72.30	$72.30
Purchase #4	$124.92	4.627%	$130.7	$130.70	$130.70	$130.70
Purchase #5	$210.48	11.433%	$234.5442	$234.54	$234.55	$234.50
Purchase #6	$182.73	4.249%	$190.4942	$190.49	$190.50	$190.50
Purchase #7	$146.35	12.816%	$165.1062	$165.11	$165.10	$165.10
7 purchase totals =	$1,073.85		$1,166.0350	$1,166.03	$1,166.05	$1,166.00