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	$31.90	11.567%	$35.5899	$35.59	$35.60	$35.60
Purchase #2	$94.35	3.711%	$97.8513	$97.85	$97.85	$97.90
Purchase #3	$63.93	5.273%	$67.301	$67.30	$67.30	$67.30
Purchase #4	$169.86	12.870%	$191.721	$191.72	$191.70	$191.70
Purchase #5	$247.50	4.213%	$257.9272	$257.93	$257.95	$257.90
Purchase #6	$83.37	7.105%	$89.2934	$89.29	$89.30	$89.30
Purchase #7	$105.83	9.168%	$115.5325	$115.53	$115.55	$115.50
7 purchase totals =	$796.74		$855.2163	$855.21	$855.25	$855.20