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	$202.64	7.526%	$217.8907	$217.89	$217.90	$217.90
Purchase #2	$134.65	7.192%	$144.334	$144.33	$144.35	$144.30
Purchase #3	$37.56	4.265%	$39.1619	$39.16	$39.15	$39.20
Purchase #4	$234.50	3.692%	$243.1577	$243.16	$243.15	$243.20
Purchase #5	$139.38	3.582%	$144.3726	$144.37	$144.35	$144.40
Purchase #6	$128.48	3.381%	$132.8239	$132.82	$132.80	$132.80
Purchase #7	$191.70	13.437%	$217.4587	$217.46	$217.45	$217.50
7 purchase totals =	$1,068.91		$1,139.1995	$1,139.19	$1,139.15	$1,139.30