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	$141.95	5.819%	$150.2101	$150.21	$150.20	$150.20
Purchase #2	$190.78	5.181%	$200.6643	$200.66	$200.65	$200.70
Purchase #3	$168.88	3.174%	$174.2403	$174.24	$174.25	$174.20
Purchase #4	$215.49	8.827%	$234.5113	$234.51	$234.50	$234.50
Purchase #5	$46.45	3.756%	$48.1947	$48.19	$48.20	$48.20
Purchase #6	$59.78	10.816%	$66.2458	$66.25	$66.25	$66.20
Purchase #7	$129.58	10.721%	$143.4723	$143.47	$143.45	$143.50
7 purchase totals =	$952.91		$1,017.5388	$1,017.53	$1,017.50	$1,017.50