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	$239.80	6.863%	$256.2575	$256.26	$256.25	$256.30
Purchase #2	$112.49	3.477%	$116.4013	$116.40	$116.40	$116.40
Purchase #3	$17.74	13.436%	$20.1235	$20.12	$20.10	$20.10
Purchase #4	$7.51	10.631%	$8.3084	$8.31	$8.30	$8.30
Purchase #5	$169.81	6.670%	$181.1363	$181.14	$181.15	$181.10
Purchase #6	$76.27	3.385%	$78.8517	$78.85	$78.85	$78.90
Purchase #7	$37.84	10.511%	$41.8174	$41.82	$41.80	$41.80
7 purchase totals =	$661.46		$702.8961	$702.90	$702.85	$702.90