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	$191.34	12.555%	$215.3627	$215.36	$215.35	$215.40
Purchase #2	$106.29	13.381%	$120.5127	$120.51	$120.50	$120.50
Purchase #3	$33.81	13.563%	$38.3957	$38.40	$38.40	$38.40
Purchase #4	$67.28	13.535%	$76.3863	$76.39	$76.40	$76.40
Purchase #5	$39.65	10.724%	$43.9021	$43.90	$43.90	$43.90
Purchase #6	$161.37	5.392%	$170.0711	$170.07	$170.05	$170.10
Purchase #7	$65.42	10.145%	$72.0569	$72.06	$72.05	$72.10
7 purchase totals =	$665.16		$736.6875	$736.69	$736.65	$736.80