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	$180.59	6.407%	$192.1604	$192.16	$192.15	$192.20
Purchase #2	$136.34	7.507%	$146.575	$146.58	$146.60	$146.60
Purchase #3	$120.73	3.167%	$124.5535	$124.55	$124.55	$124.60
Purchase #4	$33.34	9.176%	$36.3993	$36.40	$36.40	$36.40
Purchase #5	$155.26	11.322%	$172.8385	$172.84	$172.85	$172.80
Purchase #6	$111.54	10.462%	$123.2093	$123.21	$123.20	$123.20
Purchase #7	$228.51	10.207%	$251.834	$251.83	$251.85	$251.80
7 purchase totals =	$966.31		$1,047.5700	$1,047.57	$1,047.60	$1,047.60