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	$21.26	11.330%	$23.6688	$23.67	$23.65	$23.70
Purchase #2	$222.74	8.617%	$241.9335	$241.93	$241.95	$241.90
Purchase #3	$179.54	9.206%	$196.0685	$196.07	$196.05	$196.10
Purchase #4	$31.29	13.774%	$35.5999	$35.60	$35.60	$35.60
Purchase #5	$59.32	12.548%	$66.7635	$66.76	$66.75	$66.80
Purchase #6	$183.92	4.341%	$191.904	$191.90	$191.90	$191.90
Purchase #7	$228.99	13.599%	$260.1304	$260.13	$260.15	$260.10
7 purchase totals =	$927.06		$1,016.0686	$1,016.06	$1,016.05	$1,016.10