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	$44.73	3.223%	$46.1716	$46.17	$46.15	$46.20
Purchase #2	$146.52	13.105%	$165.7214	$165.72	$165.70	$165.70
Purchase #3	$31.87	9.711%	$34.9649	$34.96	$34.95	$35.00
Purchase #4	$182.80	4.566%	$191.1466	$191.15	$191.15	$191.10
Purchase #5	$88.80	12.866%	$100.225	$100.23	$100.25	$100.20
Purchase #6	$122.67	7.451%	$131.8101	$131.81	$131.80	$131.80
Purchase #7	$124.71	13.570%	$141.6331	$141.63	$141.65	$141.60
7 purchase totals =	$742.10		$811.6727	$811.67	$811.65	$811.60