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	$144.71	8.746%	$157.3663	$157.37	$157.35	$157.40
Purchase #2	$122.77	3.837%	$127.4807	$127.48	$127.50	$127.50
Purchase #3	$167.77	6.870%	$179.2958	$179.30	$179.30	$179.30
Purchase #4	$14.78	13.134%	$16.7212	$16.72	$16.70	$16.70
Purchase #5	$81.96	4.724%	$85.8318	$85.83	$85.85	$85.80
Purchase #6	$146.99	12.572%	$165.4696	$165.47	$165.45	$165.50
Purchase #7	$31.45	7.421%	$33.7839	$33.78	$33.80	$33.80
7 purchase totals =	$710.43		$765.9493	$765.95	$765.95	$766.00