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	$217.78	4.428%	$227.4233	$227.42	$227.40	$227.40
Purchase #2	$28.79	9.332%	$31.4767	$31.48	$31.50	$31.50
Purchase #3	$244.58	11.857%	$273.5799	$273.58	$273.60	$273.60
Purchase #4	$201.34	13.541%	$228.6034	$228.60	$228.60	$228.60
Purchase #5	$121.85	3.389%	$125.9795	$125.98	$126.00	$126.00
Purchase #6	$72.33	8.238%	$78.2885	$78.29	$78.30	$78.30
Purchase #7	$105.58	12.859%	$119.1565	$119.16	$119.15	$119.20
7 purchase totals =	$992.25		$1,084.5078	$1,084.51	$1,084.55	$1,084.60