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	$219.65	5.268%	$231.2212	$231.22	$231.20	$231.20
Purchase #2	$149.78	5.694%	$158.3085	$158.31	$158.30	$158.30
Purchase #3	$201.52	11.799%	$225.2973	$225.30	$225.30	$225.30
Purchase #4	$95.38	5.761%	$100.8748	$100.87	$100.85	$100.90
Purchase #5	$227.52	5.406%	$239.8197	$239.82	$239.80	$239.80
Purchase #6	$237.97	11.321%	$264.9106	$264.91	$264.90	$264.90
Purchase #7	$62.72	4.605%	$65.6083	$65.61	$65.60	$65.60
7 purchase totals =	$1,194.54		$1,286.0404	$1,286.04	$1,285.95	$1,286.00