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	$55.42	11.696%	$61.9019	$61.90	$61.90	$61.90
Purchase #2	$130.83	6.375%	$139.1704	$139.17	$139.15	$139.20
Purchase #3	$182.27	5.634%	$192.5391	$192.54	$192.55	$192.50
Purchase #4	$247.38	5.387%	$260.7064	$260.71	$260.70	$260.70
Purchase #5	$12.41	3.859%	$12.8889	$12.89	$12.90	$12.90
Purchase #6	$150.62	12.171%	$168.952	$168.95	$168.95	$169.00
Purchase #7	$81.26	13.682%	$92.378	$92.38	$92.40	$92.40
7 purchase totals =	$860.19		$928.5367	$928.54	$928.55	$928.60