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	$146.63	8.466%	$159.0437	$159.04	$159.05	$159.00
Purchase #2	$102.89	8.211%	$111.3383	$111.34	$111.35	$111.30
Purchase #3	$37.97	5.789%	$40.1681	$40.17	$40.15	$40.20
Purchase #4	$214.42	4.682%	$224.4591	$224.46	$224.45	$224.50
Purchase #5	$33.34	7.130%	$35.7171	$35.72	$35.70	$35.70
Purchase #6	$36.55	4.855%	$38.3245	$38.32	$38.30	$38.30
Purchase #7	$115.51	13.791%	$131.44	$131.44	$131.45	$131.40
7 purchase totals =	$687.31		$740.4908	$740.49	$740.45	$740.40