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	$175.83	13.818%	$200.1262	$200.13	$200.15	$200.10
Purchase #2	$215.34	6.116%	$228.5102	$228.51	$228.50	$228.50
Purchase #3	$93.97	11.855%	$105.1101	$105.11	$105.10	$105.10
Purchase #4	$161.82	13.598%	$183.8243	$183.82	$183.80	$183.80
Purchase #5	$229.82	11.161%	$255.4702	$255.47	$255.45	$255.50
Purchase #6	$222.67	3.351%	$230.1317	$230.13	$230.15	$230.10
Purchase #7	$87.32	11.477%	$97.3417	$97.34	$97.35	$97.30
7 purchase totals =	$1,186.77		$1,300.5144	$1,300.51	$1,300.50	$1,300.40