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	$48.47	7.519%	$52.1145	$52.11	$52.10	$52.10
Purchase #2	$93.32	8.755%	$101.4902	$101.49	$101.50	$101.50
Purchase #3	$105.46	11.816%	$117.9212	$117.92	$117.90	$117.90
Purchase #4	$211.37	5.173%	$222.3042	$222.30	$222.30	$222.30
Purchase #5	$105.83	11.380%	$117.8735	$117.87	$117.85	$117.90
Purchase #6	$95.37	5.726%	$100.8309	$100.83	$100.85	$100.80
Purchase #7	$216.56	10.834%	$240.0221	$240.02	$240.00	$240.00
7 purchase totals =	$876.38		$952.5566	$952.54	$952.50	$952.50