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	$141.80	7.543%	$152.496	$152.50	$152.50	$152.50
Purchase #2	$247.67	3.265%	$255.7564	$255.76	$255.75	$255.80
Purchase #3	$103.76	9.660%	$113.7832	$113.78	$113.80	$113.80
Purchase #4	$227.49	12.236%	$255.3257	$255.33	$255.35	$255.30
Purchase #5	$221.54	11.291%	$246.5541	$246.55	$246.55	$246.60
Purchase #6	$246.74	9.265%	$269.6005	$269.60	$269.60	$269.60
Purchase #7	$33.85	9.426%	$37.0407	$37.04	$37.05	$37.00
7 purchase totals =	$1,222.85		$1,330.5566	$1,330.56	$1,330.60	$1,330.60