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	$200.93	10.801%	$222.6324	$222.63	$222.65	$222.60
Purchase #2	$81.73	10.646%	$90.431	$90.43	$90.45	$90.40
Purchase #3	$43.82	12.508%	$49.301	$49.30	$49.30	$49.30
Purchase #4	$135.31	11.740%	$151.1954	$151.20	$151.20	$151.20
Purchase #5	$33.89	6.338%	$36.0379	$36.04	$36.05	$36.00
Purchase #6	$33.49	9.256%	$36.5898	$36.59	$36.60	$36.60
Purchase #7	$76.86	13.477%	$87.2184	$87.22	$87.20	$87.20
7 purchase totals =	$606.03		$673.4059	$673.41	$673.45	$673.30