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	$101.31	8.171%	$109.588	$109.59	$109.60	$109.60
Purchase #2	$107.62	3.474%	$111.3587	$111.36	$111.35	$111.40
Purchase #3	$40.34	13.518%	$45.7932	$45.79	$45.80	$45.80
Purchase #4	$127.60	3.122%	$131.5837	$131.58	$131.60	$131.60
Purchase #5	$35.32	6.396%	$37.5791	$37.58	$37.60	$37.60
Purchase #6	$12.39	3.614%	$12.8378	$12.84	$12.85	$12.80
Purchase #7	$21.96	5.519%	$23.172	$23.17	$23.15	$23.20
7 purchase totals =	$446.54		$471.9125	$471.91	$471.95	$472.00