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	$41.27	12.237%	$46.3202	$46.32	$46.30	$46.30
Purchase #2	$195.52	11.518%	$218.04	$218.04	$218.05	$218.00
Purchase #3	$236.61	6.839%	$252.7918	$252.79	$252.80	$252.80
Purchase #4	$83.38	8.567%	$90.5232	$90.52	$90.50	$90.50
Purchase #5	$140.92	8.419%	$152.7841	$152.78	$152.80	$152.80
Purchase #6	$102.31	13.587%	$116.2109	$116.21	$116.20	$116.20
Purchase #7	$250.67	6.164%	$266.1213	$266.12	$266.10	$266.10
7 purchase totals =	$1,050.68		$1,142.7915	$1,142.78	$1,142.75	$1,142.70