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	$245.54	11.390%	$273.507	$273.51	$273.50	$273.50
Purchase #2	$161.60	12.697%	$182.1184	$182.12	$182.10	$182.10
Purchase #3	$222.75	13.756%	$253.3915	$253.39	$253.40	$253.40
Purchase #4	$177.88	7.155%	$190.6073	$190.61	$190.60	$190.60
Purchase #5	$152.94	9.624%	$167.6589	$167.66	$167.65	$167.70
Purchase #6	$94.90	8.261%	$102.7397	$102.74	$102.75	$102.70
Purchase #7	$234.52	9.107%	$255.8777	$255.88	$255.90	$255.90
7 purchase totals =	$1,290.13		$1,425.9005	$1,425.91	$1,425.90	$1,425.90