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	$210.54	4.513%	$220.0417	$220.04	$220.05	$220.00
Purchase #2	$244.37	4.500%	$255.3667	$255.37	$255.35	$255.40
Purchase #3	$13.60	3.727%	$14.1069	$14.11	$14.10	$14.10
Purchase #4	$87.51	8.362%	$94.8276	$94.83	$94.85	$94.80
Purchase #5	$82.73	10.555%	$91.4622	$91.46	$91.45	$91.50
Purchase #6	$111.90	11.413%	$124.6711	$124.67	$124.65	$124.70
Purchase #7	$50.71	7.553%	$54.5401	$54.54	$54.55	$54.50
7 purchase totals =	$801.36		$855.0163	$855.02	$855.00	$855.00