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	$41.57	12.279%	$46.6744	$46.67	$46.65	$46.70
Purchase #2	$67.59	6.277%	$71.8326	$71.83	$71.85	$71.80
Purchase #3	$146.51	7.706%	$157.8001	$157.80	$157.80	$157.80
Purchase #4	$140.63	9.724%	$154.3049	$154.30	$154.30	$154.30
Purchase #5	$84.95	6.516%	$90.4853	$90.49	$90.50	$90.50
Purchase #6	$67.85	6.144%	$72.0187	$72.02	$72.00	$72.00
Purchase #7	$139.59	3.147%	$143.9829	$143.98	$144.00	$144.00
7 purchase totals =	$688.69		$737.0989	$737.09	$737.10	$737.10