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	$9.25	12.827%	$10.4365	$10.44	$10.45	$10.40
Purchase #2	$29.49	13.746%	$33.5437	$33.54	$33.55	$33.50
Purchase #3	$38.78	7.670%	$41.7544	$41.75	$41.75	$41.80
Purchase #4	$91.33	9.283%	$99.8082	$99.81	$99.80	$99.80
Purchase #5	$110.88	7.344%	$119.023	$119.02	$119.00	$119.00
Purchase #6	$77.87	11.405%	$86.7511	$86.75	$86.75	$86.80
Purchase #7	$70.92	10.550%	$78.4021	$78.40	$78.40	$78.40
7 purchase totals =	$428.52		$469.7190	$469.71	$469.70	$469.70