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	$207.43	3.726%	$215.1588	$215.16	$215.15	$215.20
Purchase #2	$87.51	3.488%	$90.5623	$90.56	$90.55	$90.60
Purchase #3	$44.57	6.817%	$47.6083	$47.61	$47.60	$47.60
Purchase #4	$144.53	8.639%	$157.0159	$157.02	$157.00	$157.00
Purchase #5	$82.42	4.663%	$86.2632	$86.26	$86.25	$86.30
Purchase #6	$127.57	12.590%	$143.6311	$143.63	$143.65	$143.60
Purchase #7	$31.25	5.491%	$32.9659	$32.97	$32.95	$33.00
7 purchase totals =	$725.28		$773.2055	$773.21	$773.15	$773.30