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	$141.72	10.472%	$156.5609	$156.56	$156.55	$156.60
Purchase #2	$126.90	13.387%	$143.8881	$143.89	$143.90	$143.90
Purchase #3	$52.35	10.238%	$57.7096	$57.71	$57.70	$57.70
Purchase #4	$160.54	11.488%	$178.9828	$178.98	$179.00	$179.00
Purchase #5	$161.48	6.489%	$171.9584	$171.96	$171.95	$172.00
Purchase #6	$60.53	5.754%	$64.0129	$64.01	$64.00	$64.00
Purchase #7	$141.45	8.762%	$153.8438	$153.84	$153.85	$153.80
7 purchase totals =	$844.97		$926.9565	$926.95	$926.95	$927.00