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	$30.96	8.300%	$33.5297	$33.53	$33.55	$33.50
Purchase #2	$29.79	7.496%	$32.0231	$32.02	$32.00	$32.00
Purchase #3	$104.38	12.541%	$117.4703	$117.47	$117.45	$117.50
Purchase #4	$59.28	7.805%	$63.9068	$63.91	$63.90	$63.90
Purchase #5	$68.38	4.748%	$71.6267	$71.63	$71.65	$71.60
Purchase #6	$18.49	9.864%	$20.3139	$20.31	$20.30	$20.30
Purchase #7	$49.52	12.206%	$55.5644	$55.56	$55.55	$55.60
7 purchase totals =	$360.80		$394.4349	$394.43	$394.40	$394.40