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	$185.73	4.304%	$193.7238	$193.72	$193.70	$193.70
Purchase #2	$103.70	4.871%	$108.7512	$108.75	$108.75	$108.80
Purchase #3	$56.49	9.238%	$61.7085	$61.71	$61.70	$61.70
Purchase #4	$107.36	4.240%	$111.9121	$111.91	$111.90	$111.90
Purchase #5	$102.61	9.266%	$112.1178	$112.12	$112.10	$112.10
Purchase #6	$161.46	7.139%	$172.9866	$172.99	$173.00	$173.00
Purchase #7	$125.96	12.329%	$141.4896	$141.49	$141.50	$141.50
7 purchase totals =	$843.31		$902.6896	$902.69	$902.65	$902.70