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	$102.35	8.869%	$111.4274	$111.43	$111.45	$111.40
Purchase #2	$172.66	11.236%	$192.0601	$192.06	$192.05	$192.10
Purchase #3	$184.28	8.834%	$200.5593	$200.56	$200.55	$200.60
Purchase #4	$130.34	5.294%	$137.2402	$137.24	$137.25	$137.20
Purchase #5	$175.93	5.650%	$185.87	$185.87	$185.85	$185.90
Purchase #6	$177.91	6.273%	$189.0703	$189.07	$189.05	$189.10
Purchase #7	$149.51	7.340%	$160.484	$160.48	$160.50	$160.50
7 purchase totals =	$1,092.98		$1,176.7113	$1,176.71	$1,176.70	$1,176.80