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	$244.36	4.666%	$255.7618	$255.76	$255.75	$255.80
Purchase #2	$119.47	8.787%	$129.9678	$129.97	$129.95	$130.00
Purchase #3	$143.45	5.128%	$150.8061	$150.81	$150.80	$150.80
Purchase #4	$171.94	3.821%	$178.5098	$178.51	$178.50	$178.50
Purchase #5	$197.56	12.130%	$221.524	$221.52	$221.50	$221.50
Purchase #6	$35.89	13.435%	$40.7118	$40.71	$40.70	$40.70
Purchase #7	$24.92	11.307%	$27.7377	$27.74	$27.75	$27.70
7 purchase totals =	$937.59		$1,005.0190	$1,005.02	$1,004.95	$1,005.00