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	$226.57	9.500%	$248.0942	$248.09	$248.10	$248.10
Purchase #2	$203.91	10.576%	$225.4755	$225.48	$225.50	$225.50
Purchase #3	$232.30	10.537%	$256.7775	$256.78	$256.80	$256.80
Purchase #4	$42.56	6.781%	$45.446	$45.45	$45.45	$45.40
Purchase #5	$182.93	9.810%	$200.8754	$200.88	$200.90	$200.90
Purchase #6	$13.38	3.557%	$13.8559	$13.86	$13.85	$13.90
Purchase #7	$244.84	11.766%	$273.6479	$273.65	$273.65	$273.60
7 purchase totals =	$1,146.49		$1,264.1724	$1,264.19	$1,264.25	$1,264.20