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	$237.57	4.256%	$247.681	$247.68	$247.70	$247.70
Purchase #2	$37.63	7.513%	$40.4571	$40.46	$40.45	$40.50
Purchase #3	$17.72	8.171%	$19.1679	$19.17	$19.15	$19.20
Purchase #4	$11.86	11.304%	$13.2007	$13.20	$13.20	$13.20
Purchase #5	$238.37	5.168%	$250.689	$250.69	$250.70	$250.70
Purchase #6	$244.70	11.749%	$273.4498	$273.45	$273.45	$273.40
Purchase #7	$75.89	9.224%	$82.8901	$82.89	$82.90	$82.90
7 purchase totals =	$863.74		$927.5356	$927.54	$927.55	$927.60