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	$128.67	11.479%	$143.44	$143.44	$143.45	$143.40
Purchase #2	$209.32	5.623%	$221.0901	$221.09	$221.10	$221.10
Purchase #3	$162.33	6.310%	$172.573	$172.57	$172.55	$172.60
Purchase #4	$250.68	9.663%	$274.9032	$274.90	$274.90	$274.90
Purchase #5	$140.93	10.256%	$155.3838	$155.38	$155.40	$155.40
Purchase #6	$131.87	8.738%	$143.3928	$143.39	$143.40	$143.40
Purchase #7	$134.28	11.828%	$150.1626	$150.16	$150.15	$150.20
7 purchase totals =	$1,158.08		$1,260.9455	$1,260.93	$1,260.95	$1,261.00