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	$57.82	9.762%	$63.4644	$63.46	$63.45	$63.50
Purchase #2	$143.54	3.307%	$148.2869	$148.29	$148.30	$148.30
Purchase #3	$93.87	13.595%	$106.6316	$106.63	$106.65	$106.60
Purchase #4	$42.68	5.714%	$45.1187	$45.12	$45.10	$45.10
Purchase #5	$141.59	10.291%	$156.161	$156.16	$156.15	$156.20
Purchase #6	$183.36	3.810%	$190.346	$190.35	$190.35	$190.30
Purchase #7	$229.44	11.172%	$255.073	$255.07	$255.05	$255.10
7 purchase totals =	$892.30		$965.0816	$965.08	$965.05	$965.10