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	$54.29	8.871%	$59.1061	$59.11	$59.10	$59.10
Purchase #2	$246.83	7.688%	$265.8063	$265.81	$265.80	$265.80
Purchase #3	$135.29	7.785%	$145.8223	$145.82	$145.80	$145.80
Purchase #4	$121.27	10.225%	$133.6699	$133.67	$133.65	$133.70
Purchase #5	$41.53	8.597%	$45.1003	$45.10	$45.10	$45.10
Purchase #6	$239.52	7.266%	$256.9235	$256.92	$256.90	$256.90
Purchase #7	$117.25	9.652%	$128.567	$128.57	$128.55	$128.60
7 purchase totals =	$955.98		$1,034.9954	$1,035.00	$1,034.90	$1,035.00