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	$33.51	11.341%	$37.3104	$37.31	$37.30	$37.30
Purchase #2	$134.99	12.509%	$151.8759	$151.88	$151.90	$151.90
Purchase #3	$35.27	3.439%	$36.4829	$36.48	$36.50	$36.50
Purchase #4	$80.93	3.481%	$83.7472	$83.75	$83.75	$83.70
Purchase #5	$105.56	7.673%	$113.6596	$113.66	$113.65	$113.70
Purchase #6	$160.37	7.455%	$172.3256	$172.33	$172.35	$172.30
Purchase #7	$13.95	5.718%	$14.7477	$14.75	$14.75	$14.70
7 purchase totals =	$564.58		$610.1493	$610.16	$610.20	$610.10