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	$97.81	4.452%	$102.1645	$102.16	$102.15	$102.20
Purchase #2	$32.25	10.119%	$35.5134	$35.51	$35.50	$35.50
Purchase #3	$49.60	11.644%	$55.3754	$55.38	$55.40	$55.40
Purchase #4	$132.95	11.327%	$148.0092	$148.01	$148.00	$148.00
Purchase #5	$146.65	12.781%	$165.3933	$165.39	$165.40	$165.40
Purchase #6	$59.68	6.207%	$63.3843	$63.38	$63.40	$63.40
Purchase #7	$89.68	6.468%	$95.4805	$95.48	$95.50	$95.50
7 purchase totals =	$608.62		$665.3206	$665.31	$665.35	$665.40