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	$134.87	5.174%	$141.8482	$141.85	$141.85	$141.80
Purchase #2	$176.80	12.499%	$198.8982	$198.90	$198.90	$198.90
Purchase #3	$197.35	11.367%	$219.7828	$219.78	$219.80	$219.80
Purchase #4	$33.41	13.470%	$37.9103	$37.91	$37.90	$37.90
Purchase #5	$139.82	3.755%	$145.0702	$145.07	$145.05	$145.10
Purchase #6	$34.83	6.748%	$37.1803	$37.18	$37.20	$37.20
Purchase #7	$190.37	3.807%	$197.6174	$197.62	$197.60	$197.60
7 purchase totals =	$907.45		$978.3074	$978.31	$978.30	$978.30