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	$11.33	4.822%	$11.8763	$11.88	$11.90	$11.90
Purchase #2	$58.49	9.204%	$63.8734	$63.87	$63.85	$63.90
Purchase #3	$29.63	8.861%	$32.2555	$32.26	$32.25	$32.30
Purchase #4	$141.95	6.322%	$150.9241	$150.92	$150.90	$150.90
Purchase #5	$225.68	3.494%	$233.5653	$233.57	$233.55	$233.60
Purchase #6	$71.34	7.131%	$76.4273	$76.43	$76.45	$76.40
Purchase #7	$36.89	10.626%	$40.8099	$40.81	$40.80	$40.80
7 purchase totals =	$575.31		$609.7318	$609.74	$609.70	$609.80