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	$105.28	11.160%	$117.0292	$117.03	$117.05	$117.00
Purchase #2	$37.55	7.385%	$40.3231	$40.32	$40.30	$40.30
Purchase #3	$92.99	13.612%	$105.6478	$105.65	$105.65	$105.60
Purchase #4	$32.77	9.602%	$35.9166	$35.92	$35.90	$35.90
Purchase #5	$30.81	12.480%	$34.6551	$34.66	$34.65	$34.70
Purchase #6	$70.37	8.654%	$76.4598	$76.46	$76.45	$76.50
Purchase #7	$132.41	7.163%	$141.8945	$141.89	$141.90	$141.90
7 purchase totals =	$502.18		$551.9261	$551.93	$551.90	$551.90