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	$166.92	3.147%	$172.173	$172.17	$172.15	$172.20
Purchase #2	$210.66	9.810%	$231.3257	$231.33	$231.35	$231.30
Purchase #3	$247.26	10.642%	$273.5734	$273.57	$273.55	$273.60
Purchase #4	$245.29	11.532%	$273.5768	$273.58	$273.60	$273.60
Purchase #5	$89.66	13.323%	$101.6054	$101.61	$101.60	$101.60
Purchase #6	$119.60	3.434%	$123.7071	$123.71	$123.70	$123.70
Purchase #7	$54.34	11.353%	$60.5092	$60.51	$60.50	$60.50
7 purchase totals =	$1,133.73		$1,236.4706	$1,236.48	$1,236.45	$1,236.50