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	$42.29	6.475%	$45.0283	$45.03	$45.05	$45.00
Purchase #2	$50.54	13.184%	$57.2032	$57.20	$57.20	$57.20
Purchase #3	$166.46	3.731%	$172.6706	$172.67	$172.65	$172.70
Purchase #4	$243.47	12.170%	$273.1003	$273.10	$273.10	$273.10
Purchase #5	$125.60	13.624%	$142.7117	$142.71	$142.70	$142.70
Purchase #6	$208.49	12.421%	$234.3865	$234.39	$234.40	$234.40
Purchase #7	$134.79	8.615%	$146.4022	$146.40	$146.40	$146.40
7 purchase totals =	$971.64		$1,071.5028	$1,071.50	$1,071.50	$1,071.50