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	$231.27	4.832%	$242.445	$242.45	$242.45	$242.40
Purchase #2	$155.47	9.661%	$170.49	$170.49	$170.50	$170.50
Purchase #3	$95.88	13.822%	$109.1325	$109.13	$109.15	$109.10
Purchase #4	$20.83	8.117%	$22.5208	$22.52	$22.50	$22.50
Purchase #5	$78.52	9.561%	$86.0273	$86.03	$86.05	$86.00
Purchase #6	$118.63	3.166%	$122.3858	$122.39	$122.40	$122.40
Purchase #7	$236.48	11.562%	$263.8218	$263.82	$263.80	$263.80
7 purchase totals =	$937.08		$1,016.8232	$1,016.83	$1,016.85	$1,016.70