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	$223.73	10.578%	$247.3962	$247.40	$247.40	$247.40
Purchase #2	$155.60	6.160%	$165.185	$165.19	$165.20	$165.20
Purchase #3	$121.74	12.829%	$137.358	$137.36	$137.35	$137.40
Purchase #4	$40.94	11.134%	$45.4983	$45.50	$45.50	$45.50
Purchase #5	$205.45	4.205%	$214.0892	$214.09	$214.10	$214.10
Purchase #6	$75.45	4.189%	$78.6106	$78.61	$78.60	$78.60
Purchase #7	$246.69	5.562%	$260.4109	$260.41	$260.40	$260.40
7 purchase totals =	$1,069.60		$1,148.5482	$1,148.56	$1,148.55	$1,148.60