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	$55.55	7.514%	$59.724	$59.72	$59.70	$59.70
Purchase #2	$191.49	13.146%	$216.6633	$216.66	$216.65	$216.70
Purchase #3	$94.86	8.135%	$102.5769	$102.58	$102.60	$102.60
Purchase #4	$228.69	5.604%	$241.5058	$241.51	$241.50	$241.50
Purchase #5	$118.44	11.873%	$132.5024	$132.50	$132.50	$132.50
Purchase #6	$228.72	11.444%	$254.8947	$254.89	$254.90	$254.90
Purchase #7	$29.51	3.856%	$30.6479	$30.65	$30.65	$30.60
7 purchase totals =	$947.26		$1,038.5150	$1,038.51	$1,038.50	$1,038.50