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	$40.28	13.155%	$45.5788	$45.58	$45.60	$45.60
Purchase #2	$123.33	7.811%	$132.9633	$132.96	$132.95	$133.00
Purchase #3	$102.82	12.478%	$115.6499	$115.65	$115.65	$115.60
Purchase #4	$116.28	6.504%	$123.8429	$123.84	$123.85	$123.80
Purchase #5	$100.63	10.628%	$111.325	$111.33	$111.35	$111.30
Purchase #6	$168.29	13.843%	$191.5864	$191.59	$191.60	$191.60
Purchase #7	$144.54	5.157%	$151.9939	$151.99	$152.00	$152.00
7 purchase totals =	$796.17		$872.9402	$872.94	$873.00	$872.90