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	$55.65	7.571%	$59.8633	$59.86	$59.85	$59.90
Purchase #2	$213.38	13.429%	$242.0348	$242.03	$242.05	$242.00
Purchase #3	$161.43	13.629%	$183.4313	$183.43	$183.45	$183.40
Purchase #4	$250.94	11.330%	$279.3715	$279.37	$279.35	$279.40
Purchase #5	$120.51	8.487%	$130.7377	$130.74	$130.75	$130.70
Purchase #6	$22.96	5.697%	$24.268	$24.27	$24.25	$24.30
Purchase #7	$115.44	9.659%	$126.5903	$126.59	$126.60	$126.60
7 purchase totals =	$940.31		$1,046.2969	$1,046.29	$1,046.30	$1,046.30