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	$113.37	12.208%	$127.2102	$127.21	$127.20	$127.20
Purchase #2	$44.85	5.495%	$47.3145	$47.31	$47.30	$47.30
Purchase #3	$102.43	10.839%	$113.5324	$113.53	$113.55	$113.50
Purchase #4	$131.31	11.579%	$146.5144	$146.51	$146.50	$146.50
Purchase #5	$137.34	10.426%	$151.6591	$151.66	$151.65	$151.70
Purchase #6	$92.48	12.758%	$104.2786	$104.28	$104.30	$104.30
Purchase #7	$53.91	3.509%	$55.8017	$55.80	$55.80	$55.80
7 purchase totals =	$675.69		$746.3109	$746.30	$746.30	$746.30