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	$91.94	3.142%	$94.8288	$94.83	$94.85	$94.80
Purchase #2	$105.88	12.405%	$119.0144	$119.01	$119.00	$119.00
Purchase #3	$217.67	8.528%	$236.2329	$236.23	$236.25	$236.20
Purchase #4	$92.42	7.138%	$99.0169	$99.02	$99.00	$99.00
Purchase #5	$136.97	10.289%	$151.0628	$151.06	$151.05	$151.10
Purchase #6	$12.47	6.343%	$13.261	$13.26	$13.25	$13.30
Purchase #7	$185.56	5.866%	$196.4449	$196.44	$196.45	$196.40
7 purchase totals =	$842.91		$909.8617	$909.85	$909.85	$909.80