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	$87.54	6.695%	$93.4008	$93.40	$93.40	$93.40
Purchase #2	$37.89	6.705%	$40.4305	$40.43	$40.45	$40.40
Purchase #3	$169.65	12.526%	$190.9004	$190.90	$190.90	$190.90
Purchase #4	$161.66	6.578%	$172.294	$172.29	$172.30	$172.30
Purchase #5	$63.91	13.507%	$72.5423	$72.54	$72.55	$72.50
Purchase #6	$126.98	11.769%	$141.9243	$141.92	$141.90	$141.90
Purchase #7	$47.62	5.665%	$50.3177	$50.32	$50.30	$50.30
7 purchase totals =	$695.25		$761.8100	$761.80	$761.80	$761.70