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	$215.73	9.327%	$235.8511	$235.85	$235.85	$235.90
Purchase #2	$89.49	3.777%	$92.87	$92.87	$92.85	$92.90
Purchase #3	$144.78	8.199%	$156.6505	$156.65	$156.65	$156.70
Purchase #4	$37.34	13.487%	$42.376	$42.38	$42.40	$42.40
Purchase #5	$234.66	4.182%	$244.4735	$244.47	$244.45	$244.50
Purchase #6	$32.50	13.584%	$36.9148	$36.91	$36.90	$36.90
Purchase #7	$19.32	9.761%	$21.2058	$21.21	$21.20	$21.20
7 purchase totals =	$773.82		$830.3417	$830.34	$830.30	$830.50