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	$10.59	3.192%	$10.928	$10.93	$10.95	$10.90
Purchase #2	$114.67	3.840%	$119.0733	$119.07	$119.05	$119.10
Purchase #3	$98.29	7.172%	$105.3394	$105.34	$105.35	$105.30
Purchase #4	$94.86	13.675%	$107.8321	$107.83	$107.85	$107.80
Purchase #5	$37.59	12.112%	$42.1429	$42.14	$42.15	$42.10
Purchase #6	$76.26	12.143%	$85.5203	$85.52	$85.50	$85.50
Purchase #7	$93.90	8.487%	$101.8693	$101.87	$101.85	$101.90
7 purchase totals =	$526.16		$572.7053	$572.70	$572.70	$572.60