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	$53.45	10.587%	$59.1088	$59.11	$59.10	$59.10
Purchase #2	$131.64	13.185%	$148.9967	$149.00	$149.00	$149.00
Purchase #3	$126.66	12.800%	$142.8725	$142.87	$142.85	$142.90
Purchase #4	$132.45	8.327%	$143.4791	$143.48	$143.50	$143.50
Purchase #5	$80.40	9.570%	$88.0943	$88.09	$88.10	$88.10
Purchase #6	$138.37	8.324%	$149.8879	$149.89	$149.90	$149.90
Purchase #7	$91.82	8.432%	$99.5623	$99.56	$99.55	$99.60
7 purchase totals =	$754.79		$832.0016	$832.00	$832.00	$832.10