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	$81.65	13.545%	$92.7095	$92.71	$92.70	$92.70
Purchase #2	$124.86	9.413%	$136.6131	$136.61	$136.60	$136.60
Purchase #3	$138.35	5.725%	$146.2705	$146.27	$146.25	$146.30
Purchase #4	$98.76	12.495%	$111.1001	$111.10	$111.10	$111.10
Purchase #5	$44.52	6.500%	$47.4138	$47.41	$47.40	$47.40
Purchase #6	$15.94	4.561%	$16.667	$16.67	$16.65	$16.70
Purchase #7	$140.51	4.472%	$146.7936	$146.79	$146.80	$146.80
7 purchase totals =	$644.59		$697.5676	$697.56	$697.50	$697.60