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	$216.39	5.128%	$227.4865	$227.49	$227.50	$227.50
Purchase #2	$136.32	6.775%	$145.5557	$145.56	$145.55	$145.60
Purchase #3	$28.69	12.665%	$32.3236	$32.32	$32.30	$32.30
Purchase #4	$235.48	3.279%	$243.2014	$243.20	$243.20	$243.20
Purchase #5	$200.48	11.660%	$223.856	$223.86	$223.85	$223.90
Purchase #6	$105.65	10.744%	$117.001	$117.00	$117.00	$117.00
Purchase #7	$88.38	10.270%	$97.4566	$97.46	$97.45	$97.50
7 purchase totals =	$1,011.39		$1,086.8808	$1,086.89	$1,086.85	$1,087.00