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	$190.49	13.292%	$215.8099	$215.81	$215.80	$215.80
Purchase #2	$52.61	9.230%	$57.4659	$57.47	$57.45	$57.50
Purchase #3	$40.95	6.833%	$43.7481	$43.75	$43.75	$43.70
Purchase #4	$215.98	6.484%	$229.9841	$229.98	$230.00	$230.00
Purchase #5	$224.27	3.850%	$232.9044	$232.90	$232.90	$232.90
Purchase #6	$131.87	10.365%	$145.5383	$145.54	$145.55	$145.50
Purchase #7	$232.67	9.764%	$255.3879	$255.39	$255.40	$255.40
7 purchase totals =	$1,088.84		$1,180.8386	$1,180.84	$1,180.85	$1,180.80