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	$215.65	3.133%	$222.4063	$222.41	$222.40	$222.40
Purchase #2	$141.45	7.373%	$151.8791	$151.88	$151.90	$151.90
Purchase #3	$242.87	8.352%	$263.1545	$263.15	$263.15	$263.20
Purchase #4	$74.29	10.660%	$82.2093	$82.21	$82.20	$82.20
Purchase #5	$248.53	11.387%	$276.8301	$276.83	$276.85	$276.80
Purchase #6	$10.83	8.703%	$11.7725	$11.77	$11.75	$11.80
Purchase #7	$27.90	13.464%	$31.6565	$31.66	$31.65	$31.70
7 purchase totals =	$961.52		$1,039.9083	$1,039.91	$1,039.90	$1,040.00