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	$117.43	4.286%	$122.463	$122.46	$122.45	$122.50
Purchase #2	$90.58	11.350%	$100.8608	$100.86	$100.85	$100.90
Purchase #3	$177.68	8.113%	$192.0952	$192.10	$192.10	$192.10
Purchase #4	$218.40	7.411%	$234.5856	$234.59	$234.60	$234.60
Purchase #5	$41.68	9.306%	$45.5587	$45.56	$45.55	$45.60
Purchase #6	$95.46	4.121%	$99.3939	$99.39	$99.40	$99.40
Purchase #7	$244.81	12.676%	$275.8421	$275.84	$275.85	$275.80
7 purchase totals =	$986.04		$1,070.7993	$1,070.80	$1,070.80	$1,070.90