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	$197.50	13.161%	$223.493	$223.49	$223.50	$223.50
Purchase #2	$196.95	9.179%	$215.028	$215.03	$215.05	$215.00
Purchase #3	$28.37	4.368%	$29.6092	$29.61	$29.60	$29.60
Purchase #4	$113.50	7.769%	$122.3178	$122.32	$122.30	$122.30
Purchase #5	$141.55	12.630%	$159.4278	$159.43	$159.45	$159.40
Purchase #6	$243.32	5.585%	$256.9094	$256.91	$256.90	$256.90
Purchase #7	$32.72	4.366%	$34.1486	$34.15	$34.15	$34.10
7 purchase totals =	$953.91		$1,040.9338	$1,040.94	$1,040.95	$1,040.80