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	$125.64	7.456%	$135.0077	$135.01	$135.00	$135.00
Purchase #2	$164.89	10.479%	$182.1688	$182.17	$182.15	$182.20
Purchase #3	$85.95	10.774%	$95.2103	$95.21	$95.20	$95.20
Purchase #4	$152.54	13.158%	$172.6112	$172.61	$172.60	$172.60
Purchase #5	$92.52	10.503%	$102.2374	$102.24	$102.25	$102.20
Purchase #6	$5.41	8.829%	$5.8876	$5.89	$5.90	$5.90
Purchase #7	$100.34	11.359%	$111.7376	$111.74	$111.75	$111.70
7 purchase totals =	$727.29		$804.8606	$804.87	$804.85	$804.80