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	$133.61	13.361%	$151.4616	$151.46	$151.45	$151.50
Purchase #2	$21.66	5.570%	$22.8665	$22.87	$22.85	$22.90
Purchase #3	$31.31	4.278%	$32.6494	$32.65	$32.65	$32.60
Purchase #4	$139.55	7.597%	$150.1516	$150.15	$150.15	$150.20
Purchase #5	$10.73	7.333%	$11.5168	$11.52	$11.50	$11.50
Purchase #6	$128.57	8.240%	$139.1642	$139.16	$139.15	$139.20
Purchase #7	$23.88	5.199%	$25.1215	$25.12	$25.10	$25.10
7 purchase totals =	$489.31		$532.9316	$532.93	$532.85	$533.00