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	$133.32	11.718%	$148.9424	$148.94	$148.95	$148.90
Purchase #2	$202.29	5.767%	$213.9561	$213.96	$213.95	$214.00
Purchase #3	$45.43	11.866%	$50.8207	$50.82	$50.80	$50.80
Purchase #4	$63.50	4.473%	$66.3404	$66.34	$66.35	$66.30
Purchase #5	$45.93	3.339%	$47.4636	$47.46	$47.45	$47.50
Purchase #6	$198.41	3.784%	$205.9178	$205.92	$205.90	$205.90
Purchase #7	$217.88	11.748%	$243.4765	$243.48	$243.50	$243.50
7 purchase totals =	$906.76		$976.9175	$976.92	$976.90	$976.90