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	$221.33	13.142%	$250.4172	$250.42	$250.40	$250.40
Purchase #2	$201.67	8.130%	$218.0658	$218.07	$218.05	$218.10
Purchase #3	$247.69	4.510%	$258.8608	$258.86	$258.85	$258.90
Purchase #4	$67.67	11.615%	$75.5299	$75.53	$75.55	$75.50
Purchase #5	$164.40	7.264%	$176.342	$176.34	$176.35	$176.30
Purchase #6	$99.49	10.396%	$109.833	$109.83	$109.85	$109.80
Purchase #7	$148.32	6.801%	$158.4072	$158.41	$158.40	$158.40
7 purchase totals =	$1,150.57		$1,247.4559	$1,247.46	$1,247.45	$1,247.40