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	$212.85	8.456%	$230.8486	$230.85	$230.85	$230.80
Purchase #2	$56.61	12.273%	$63.5577	$63.56	$63.55	$63.60
Purchase #3	$80.61	12.193%	$90.4388	$90.44	$90.45	$90.40
Purchase #4	$232.54	13.147%	$263.112	$263.11	$263.10	$263.10
Purchase #5	$134.50	3.574%	$139.307	$139.31	$139.30	$139.30
Purchase #6	$10.82	9.446%	$11.8421	$11.84	$11.85	$11.80
Purchase #7	$164.98	13.817%	$187.7753	$187.78	$187.80	$187.80
7 purchase totals =	$892.91		$986.8815	$986.89	$986.90	$986.80