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	$58.39	5.165%	$61.4058	$61.41	$61.40	$61.40
Purchase #2	$75.58	4.137%	$78.7067	$78.71	$78.70	$78.70
Purchase #3	$189.41	7.660%	$203.9188	$203.92	$203.90	$203.90
Purchase #4	$141.42	13.436%	$160.4212	$160.42	$160.40	$160.40
Purchase #5	$42.38	9.253%	$46.3014	$46.30	$46.30	$46.30
Purchase #6	$141.80	13.863%	$161.4577	$161.46	$161.45	$161.50
Purchase #7	$100.52	12.320%	$112.9041	$112.90	$112.90	$112.90
7 purchase totals =	$749.50		$825.1157	$825.12	$825.05	$825.10