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	$99.79	12.273%	$112.0372	$112.04	$112.05	$112.00
Purchase #2	$15.95	13.329%	$18.076	$18.08	$18.10	$18.10
Purchase #3	$14.70	7.812%	$15.8484	$15.85	$15.85	$15.80
Purchase #4	$245.94	13.483%	$279.1001	$279.10	$279.10	$279.10
Purchase #5	$142.48	4.239%	$148.5197	$148.52	$148.50	$148.50
Purchase #6	$86.79	4.458%	$90.6591	$90.66	$90.65	$90.70
Purchase #7	$36.55	4.841%	$38.3194	$38.32	$38.30	$38.30
7 purchase totals =	$642.20		$702.5599	$702.57	$702.55	$702.50