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	$187.48	7.144%	$200.8736	$200.87	$200.85	$200.90
Purchase #2	$208.41	8.208%	$225.5163	$225.52	$225.50	$225.50
Purchase #3	$53.53	3.504%	$55.4057	$55.41	$55.40	$55.40
Purchase #4	$35.78	12.483%	$40.2464	$40.25	$40.25	$40.20
Purchase #5	$148.50	3.147%	$153.1733	$153.17	$153.15	$153.20
Purchase #6	$10.36	11.729%	$11.5751	$11.58	$11.60	$11.60
Purchase #7	$231.77	3.653%	$240.2366	$240.24	$240.25	$240.20
7 purchase totals =	$875.83		$927.0270	$927.04	$927.00	$927.00