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	$40.54	11.406%	$45.164	$45.16	$45.15	$45.20
Purchase #2	$151.34	13.785%	$172.2022	$172.20	$172.20	$172.20
Purchase #3	$243.32	4.596%	$254.503	$254.50	$254.50	$254.50
Purchase #4	$183.48	3.615%	$190.1128	$190.11	$190.10	$190.10
Purchase #5	$117.49	7.184%	$125.9305	$125.93	$125.95	$125.90
Purchase #6	$97.44	7.597%	$104.8425	$104.84	$104.85	$104.80
Purchase #7	$182.28	13.238%	$206.4102	$206.41	$206.40	$206.40
7 purchase totals =	$1,015.89		$1,099.1652	$1,099.15	$1,099.15	$1,099.10