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	$220.51	5.467%	$232.5653	$232.57	$232.55	$232.60
Purchase #2	$175.74	7.559%	$189.0242	$189.02	$189.00	$189.00
Purchase #3	$247.35	3.540%	$256.1062	$256.11	$256.10	$256.10
Purchase #4	$122.65	6.481%	$130.5989	$130.60	$130.60	$130.60
Purchase #5	$81.67	10.624%	$90.3466	$90.35	$90.35	$90.30
Purchase #6	$90.99	9.175%	$99.3383	$99.34	$99.35	$99.30
Purchase #7	$59.85	5.762%	$63.2986	$63.30	$63.30	$63.30
7 purchase totals =	$998.76		$1,061.2781	$1,061.29	$1,061.25	$1,061.20