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	$93.34	10.803%	$103.4235	$103.42	$103.40	$103.40
Purchase #2	$242.78	5.455%	$256.0236	$256.02	$256.00	$256.00
Purchase #3	$206.93	9.654%	$226.907	$226.91	$226.90	$226.90
Purchase #4	$111.66	6.440%	$118.8509	$118.85	$118.85	$118.90
Purchase #5	$59.33	3.794%	$61.581	$61.58	$61.60	$61.60
Purchase #6	$225.80	12.265%	$253.4944	$253.49	$253.50	$253.50
Purchase #7	$37.95	8.375%	$41.1283	$41.13	$41.15	$41.10
7 purchase totals =	$977.79		$1,061.4087	$1,061.40	$1,061.40	$1,061.40