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	$141.66	3.191%	$146.1804	$146.18	$146.20	$146.20
Purchase #2	$131.25	11.743%	$146.6627	$146.66	$146.65	$146.70
Purchase #3	$174.31	11.763%	$194.8141	$194.81	$194.80	$194.80
Purchase #4	$97.85	12.166%	$109.7544	$109.75	$109.75	$109.80
Purchase #5	$100.81	10.272%	$111.1652	$111.17	$111.15	$111.20
Purchase #6	$7.48	6.559%	$7.9706	$7.97	$7.95	$8.00
Purchase #7	$172.59	11.226%	$191.965	$191.97	$191.95	$192.00
7 purchase totals =	$825.95		$908.5124	$908.51	$908.45	$908.70