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	$240.43	12.209%	$269.7841	$269.78	$269.80	$269.80
Purchase #2	$20.58	9.757%	$22.588	$22.59	$22.60	$22.60
Purchase #3	$36.34	3.541%	$37.6268	$37.63	$37.65	$37.60
Purchase #4	$37.85	7.779%	$40.7944	$40.79	$40.80	$40.80
Purchase #5	$132.90	11.690%	$148.436	$148.44	$148.45	$148.40
Purchase #6	$57.47	3.264%	$59.3458	$59.35	$59.35	$59.30
Purchase #7	$212.62	5.870%	$225.1008	$225.10	$225.10	$225.10
7 purchase totals =	$738.19		$803.6759	$803.68	$803.75	$803.60