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	$47.68	4.758%	$49.9486	$49.95	$49.95	$49.90
Purchase #2	$69.68	13.250%	$78.9126	$78.91	$78.90	$78.90
Purchase #3	$49.80	13.206%	$56.3766	$56.38	$56.40	$56.40
Purchase #4	$204.51	5.624%	$216.0116	$216.01	$216.00	$216.00
Purchase #5	$123.42	5.846%	$130.6351	$130.64	$130.65	$130.60
Purchase #6	$192.31	3.419%	$198.8851	$198.89	$198.90	$198.90
Purchase #7	$73.94	11.554%	$82.483	$82.48	$82.50	$82.50
7 purchase totals =	$761.34		$813.2526	$813.26	$813.30	$813.20