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	$32.32	4.792%	$33.8688	$33.87	$33.85	$33.90
Purchase #2	$32.88	6.521%	$35.0241	$35.02	$35.00	$35.00
Purchase #3	$84.50	4.679%	$88.4538	$88.45	$88.45	$88.50
Purchase #4	$141.65	11.765%	$158.3151	$158.32	$158.30	$158.30
Purchase #5	$151.31	4.696%	$158.4155	$158.42	$158.40	$158.40
Purchase #6	$193.77	6.564%	$206.4891	$206.49	$206.50	$206.50
Purchase #7	$217.85	8.587%	$236.5568	$236.56	$236.55	$236.60
7 purchase totals =	$854.28		$917.1232	$917.13	$917.05	$917.20