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	$58.49	6.833%	$62.4866	$62.49	$62.50	$62.50
Purchase #2	$179.25	6.302%	$190.5463	$190.55	$190.55	$190.50
Purchase #3	$231.35	12.505%	$260.2803	$260.28	$260.30	$260.30
Purchase #4	$24.84	10.812%	$27.5257	$27.53	$27.55	$27.50
Purchase #5	$117.30	11.191%	$130.427	$130.43	$130.45	$130.40
Purchase #6	$118.42	4.333%	$123.5511	$123.55	$123.55	$123.60
Purchase #7	$71.82	7.481%	$77.1929	$77.19	$77.20	$77.20
7 purchase totals =	$801.47		$872.0099	$872.02	$872.10	$872.00