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	$196.84	3.111%	$202.9637	$202.96	$202.95	$203.00
Purchase #2	$132.44	9.178%	$144.5953	$144.60	$144.60	$144.60
Purchase #3	$83.75	4.734%	$87.7147	$87.71	$87.70	$87.70
Purchase #4	$140.84	7.143%	$150.9002	$150.90	$150.90	$150.90
Purchase #5	$47.77	13.828%	$54.3756	$54.38	$54.40	$54.40
Purchase #6	$84.98	6.361%	$90.3856	$90.39	$90.40	$90.40
Purchase #7	$135.72	6.479%	$144.5133	$144.51	$144.50	$144.50
7 purchase totals =	$822.34		$875.4484	$875.45	$875.45	$875.50