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	$233.92	10.828%	$259.2489	$259.25	$259.25	$259.20
Purchase #2	$25.50	3.247%	$26.328	$26.33	$26.35	$26.30
Purchase #3	$160.57	7.330%	$172.3398	$172.34	$172.35	$172.30
Purchase #4	$99.67	5.252%	$104.9047	$104.90	$104.90	$104.90
Purchase #5	$43.93	8.151%	$47.5107	$47.51	$47.50	$47.50
Purchase #6	$35.31	5.575%	$37.2785	$37.28	$37.30	$37.30
Purchase #7	$12.86	13.553%	$14.6029	$14.60	$14.60	$14.60
7 purchase totals =	$611.76		$662.2135	$662.21	$662.25	$662.10