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	$212.98	3.689%	$220.8368	$220.84	$220.85	$220.80
Purchase #2	$29.27	11.551%	$32.651	$32.65	$32.65	$32.70
Purchase #3	$144.90	4.317%	$151.1553	$151.16	$151.15	$151.20
Purchase #4	$116.61	8.682%	$126.7341	$126.73	$126.75	$126.70
Purchase #5	$120.53	13.546%	$136.857	$136.86	$136.85	$136.90
Purchase #6	$153.92	3.151%	$158.77	$158.77	$158.75	$158.80
Purchase #7	$79.37	12.755%	$89.4936	$89.49	$89.50	$89.50
7 purchase totals =	$857.58		$916.4978	$916.50	$916.50	$916.60