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	$40.91	13.408%	$46.3952	$46.40	$46.40	$46.40
Purchase #2	$88.51	13.757%	$100.6863	$100.69	$100.70	$100.70
Purchase #3	$6.94	8.433%	$7.5253	$7.53	$7.55	$7.50
Purchase #4	$132.68	6.436%	$141.2193	$141.22	$141.20	$141.20
Purchase #5	$132.79	13.799%	$151.1137	$151.11	$151.10	$151.10
Purchase #6	$151.47	13.554%	$172.0002	$172.00	$172.00	$172.00
Purchase #7	$131.90	9.234%	$144.0796	$144.08	$144.10	$144.10
7 purchase totals =	$685.20		$763.0196	$763.03	$763.05	$763.00