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	$10.31	7.409%	$11.0739	$11.07	$11.05	$11.10
Purchase #2	$39.76	13.553%	$45.1487	$45.15	$45.15	$45.10
Purchase #3	$114.28	6.330%	$121.5139	$121.51	$121.50	$121.50
Purchase #4	$209.40	6.863%	$223.7711	$223.77	$223.75	$223.80
Purchase #5	$179.67	10.700%	$198.8947	$198.89	$198.90	$198.90
Purchase #6	$50.43	6.683%	$53.8002	$53.80	$53.80	$53.80
Purchase #7	$208.97	6.616%	$222.7955	$222.80	$222.80	$222.80
7 purchase totals =	$812.82		$876.9980	$876.99	$876.95	$877.00