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	$127.42	10.491%	$140.7876	$140.79	$140.80	$140.80
Purchase #2	$90.31	11.478%	$100.6758	$100.68	$100.70	$100.70
Purchase #3	$34.48	8.445%	$37.3918	$37.39	$37.40	$37.40
Purchase #4	$38.51	5.504%	$40.6296	$40.63	$40.65	$40.60
Purchase #5	$53.80	3.321%	$55.5867	$55.59	$55.60	$55.60
Purchase #6	$179.62	12.577%	$202.2108	$202.21	$202.20	$202.20
Purchase #7	$89.33	7.183%	$95.7466	$95.75	$95.75	$95.70
7 purchase totals =	$613.47		$673.0289	$673.04	$673.10	$673.00