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	$220.31	9.667%	$241.6074	$241.61	$241.60	$241.60
Purchase #2	$71.41	5.261%	$75.1669	$75.17	$75.15	$75.20
Purchase #3	$74.83	13.819%	$85.1708	$85.17	$85.15	$85.20
Purchase #4	$144.86	7.760%	$156.1011	$156.10	$156.10	$156.10
Purchase #5	$222.70	10.654%	$246.4265	$246.43	$246.45	$246.40
Purchase #6	$70.84	10.109%	$78.0012	$78.00	$78.00	$78.00
Purchase #7	$47.44	7.313%	$50.9093	$50.91	$50.90	$50.90
7 purchase totals =	$852.39		$933.3832	$933.39	$933.35	$933.40