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	$74.61	11.165%	$82.9402	$82.94	$82.95	$82.90
Purchase #2	$54.67	10.419%	$60.3661	$60.37	$60.35	$60.40
Purchase #3	$216.37	10.262%	$238.5739	$238.57	$238.55	$238.60
Purchase #4	$88.53	7.848%	$95.4778	$95.48	$95.50	$95.50
Purchase #5	$175.79	13.633%	$199.7555	$199.76	$199.75	$199.80
Purchase #6	$136.89	13.793%	$155.7712	$155.77	$155.75	$155.80
Purchase #7	$175.56	3.762%	$182.1646	$182.16	$182.15	$182.20
7 purchase totals =	$922.42		$1,015.0493	$1,015.05	$1,015.00	$1,015.20