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	$110.54	9.409%	$120.9407	$120.94	$120.95	$120.90
Purchase #2	$201.55	10.252%	$222.2129	$222.21	$222.20	$222.20
Purchase #3	$82.37	4.255%	$85.8748	$85.87	$85.85	$85.90
Purchase #4	$197.54	5.559%	$208.5212	$208.52	$208.50	$208.50
Purchase #5	$186.87	4.628%	$195.5183	$195.52	$195.50	$195.50
Purchase #6	$47.51	10.389%	$52.4458	$52.45	$52.45	$52.40
Purchase #7	$135.54	3.257%	$139.9545	$139.95	$139.95	$140.00
7 purchase totals =	$961.92		$1,025.4682	$1,025.46	$1,025.40	$1,025.40