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	$201.41	6.810%	$215.126	$215.13	$215.15	$215.10
Purchase #2	$88.74	13.253%	$100.5007	$100.50	$100.50	$100.50
Purchase #3	$47.35	9.142%	$51.6787	$51.68	$51.70	$51.70
Purchase #4	$100.75	12.186%	$113.0274	$113.03	$113.05	$113.00
Purchase #5	$129.37	9.434%	$141.5748	$141.57	$141.55	$141.60
Purchase #6	$233.54	6.860%	$249.5608	$249.56	$249.55	$249.60
Purchase #7	$76.25	8.161%	$82.4728	$82.47	$82.45	$82.50
7 purchase totals =	$877.41		$953.9412	$953.94	$953.95	$954.00