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	$225.82	12.440%	$253.912	$253.91	$253.90	$253.90
Purchase #2	$189.53	5.763%	$200.4526	$200.45	$200.45	$200.50
Purchase #3	$133.69	6.660%	$142.5938	$142.59	$142.60	$142.60
Purchase #4	$72.37	8.431%	$78.4715	$78.47	$78.45	$78.50
Purchase #5	$172.35	10.264%	$190.04	$190.04	$190.05	$190.00
Purchase #6	$18.41	7.700%	$19.8276	$19.83	$19.85	$19.80
Purchase #7	$136.71	11.825%	$152.876	$152.88	$152.90	$152.90
7 purchase totals =	$948.88		$1,038.1735	$1,038.17	$1,038.20	$1,038.20