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	$213.56	12.672%	$240.6223	$240.62	$240.60	$240.60
Purchase #2	$208.56	4.485%	$217.9139	$217.91	$217.90	$217.90
Purchase #3	$242.26	3.165%	$249.9275	$249.93	$249.95	$249.90
Purchase #4	$73.50	13.644%	$83.5283	$83.53	$83.55	$83.50
Purchase #5	$241.79	7.375%	$259.622	$259.62	$259.60	$259.60
Purchase #6	$153.55	4.264%	$160.0974	$160.10	$160.10	$160.10
Purchase #7	$169.34	12.332%	$190.223	$190.22	$190.20	$190.20
7 purchase totals =	$1,302.56		$1,401.9344	$1,401.93	$1,401.90	$1,401.80