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	$13.62	8.480%	$14.775	$14.78	$14.80	$14.80
Purchase #2	$30.50	8.696%	$33.1523	$33.15	$33.15	$33.20
Purchase #3	$97.29	7.822%	$104.9	$104.90	$104.90	$104.90
Purchase #4	$92.47	8.579%	$100.403	$100.40	$100.40	$100.40
Purchase #5	$61.86	13.704%	$70.3373	$70.34	$70.35	$70.30
Purchase #6	$35.60	12.468%	$40.0386	$40.04	$40.05	$40.00
Purchase #7	$227.30	12.780%	$256.3489	$256.35	$256.35	$256.30
7 purchase totals =	$558.64		$619.9551	$619.96	$620.00	$619.90