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	$238.66	3.562%	$247.1611	$247.16	$247.15	$247.20
Purchase #2	$35.88	5.667%	$37.9133	$37.91	$37.90	$37.90
Purchase #3	$63.88	13.854%	$72.7299	$72.73	$72.75	$72.70
Purchase #4	$21.33	13.527%	$24.2153	$24.22	$24.20	$24.20
Purchase #5	$90.97	10.627%	$100.6374	$100.64	$100.65	$100.60
Purchase #6	$138.70	13.626%	$157.5993	$157.60	$157.60	$157.60
Purchase #7	$249.48	4.858%	$261.5997	$261.60	$261.60	$261.60
7 purchase totals =	$838.90		$901.8560	$901.86	$901.85	$901.80