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	$65.73	10.292%	$72.4949	$72.49	$72.50	$72.50
Purchase #2	$54.85	8.639%	$59.5885	$59.59	$59.60	$59.60
Purchase #3	$89.42	7.435%	$96.0684	$96.07	$96.05	$96.10
Purchase #4	$32.38	7.249%	$34.7272	$34.73	$34.75	$34.70
Purchase #5	$213.63	11.820%	$238.8811	$238.88	$238.90	$238.90
Purchase #6	$22.81	6.480%	$24.2881	$24.29	$24.30	$24.30
Purchase #7	$6.43	10.555%	$7.1087	$7.11	$7.10	$7.10
7 purchase totals =	$485.25		$533.1569	$533.16	$533.20	$533.20