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	$31.56	8.216%	$34.153	$34.15	$34.15	$34.20
Purchase #2	$34.53	7.539%	$37.1332	$37.13	$37.15	$37.10
Purchase #3	$229.80	12.527%	$258.587	$258.59	$258.60	$258.60
Purchase #4	$190.81	12.780%	$215.1955	$215.20	$215.20	$215.20
Purchase #5	$185.31	7.676%	$199.5344	$199.53	$199.55	$199.50
Purchase #6	$237.68	10.610%	$262.8978	$262.90	$262.90	$262.90
Purchase #7	$82.48	10.521%	$91.1577	$91.16	$91.15	$91.20
7 purchase totals =	$992.17		$1,098.6586	$1,098.66	$1,098.70	$1,098.70