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	$33.26	7.173%	$35.6457	$35.65	$35.65	$35.60
Purchase #2	$64.32	11.715%	$71.8551	$71.86	$71.85	$71.90
Purchase #3	$75.87	9.229%	$82.872	$82.87	$82.85	$82.90
Purchase #4	$66.67	9.558%	$73.0423	$73.04	$73.05	$73.00
Purchase #5	$159.82	4.787%	$167.4706	$167.47	$167.45	$167.50
Purchase #6	$223.38	8.109%	$241.4939	$241.49	$241.50	$241.50
Purchase #7	$146.93	7.429%	$157.8454	$157.85	$157.85	$157.80
7 purchase totals =	$770.25		$830.2250	$830.23	$830.20	$830.20