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	$202.26	4.692%	$211.75	$211.75	$211.75	$211.80
Purchase #2	$177.32	10.796%	$196.4635	$196.46	$196.45	$196.50
Purchase #3	$69.90	12.782%	$78.8346	$78.83	$78.85	$78.80
Purchase #4	$21.42	11.119%	$23.8017	$23.80	$23.80	$23.80
Purchase #5	$125.85	5.303%	$132.5238	$132.52	$132.50	$132.50
Purchase #6	$138.53	8.648%	$150.5101	$150.51	$150.50	$150.50
Purchase #7	$55.73	9.635%	$61.0996	$61.10	$61.10	$61.10
7 purchase totals =	$791.01		$854.9833	$854.97	$854.95	$855.00