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	$14.75	9.597%	$16.1656	$16.17	$16.15	$16.20
Purchase #2	$109.25	13.639%	$124.1506	$124.15	$124.15	$124.20
Purchase #3	$247.32	5.756%	$261.5557	$261.56	$261.55	$261.60
Purchase #4	$185.82	5.714%	$196.4378	$196.44	$196.45	$196.40
Purchase #5	$59.34	3.602%	$61.4774	$61.48	$61.50	$61.50
Purchase #6	$19.82	9.731%	$21.7487	$21.75	$21.75	$21.70
Purchase #7	$169.58	7.170%	$181.7389	$181.74	$181.75	$181.70
7 purchase totals =	$805.88		$863.2747	$863.29	$863.30	$863.30