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	$216.27	7.401%	$232.2761	$232.28	$232.30	$232.30
Purchase #2	$75.53	10.691%	$83.6049	$83.60	$83.60	$83.60
Purchase #3	$18.53	13.728%	$21.0738	$21.07	$21.05	$21.10
Purchase #4	$159.79	7.834%	$172.3079	$172.31	$172.30	$172.30
Purchase #5	$248.50	10.137%	$273.6904	$273.69	$273.70	$273.70
Purchase #6	$230.26	12.669%	$259.4316	$259.43	$259.45	$259.40
Purchase #7	$55.70	9.571%	$61.031	$61.03	$61.05	$61.00
7 purchase totals =	$1,004.58		$1,103.4157	$1,103.41	$1,103.45	$1,103.40