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	$124.94	12.431%	$140.4713	$140.47	$140.45	$140.50
Purchase #2	$43.32	5.230%	$45.5856	$45.59	$45.60	$45.60
Purchase #3	$88.39	13.416%	$100.2484	$100.25	$100.25	$100.20
Purchase #4	$116.25	8.812%	$126.494	$126.49	$126.50	$126.50
Purchase #5	$157.88	5.389%	$166.3882	$166.39	$166.40	$166.40
Purchase #6	$242.87	12.470%	$273.1559	$273.16	$273.15	$273.20
Purchase #7	$123.62	5.408%	$130.3054	$130.31	$130.30	$130.30
7 purchase totals =	$897.27		$982.6488	$982.66	$982.65	$982.70