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	$80.81	6.705%	$86.2283	$86.23	$86.25	$86.20
Purchase #2	$152.89	10.851%	$169.4801	$169.48	$169.50	$169.50
Purchase #3	$89.46	5.186%	$94.0994	$94.10	$94.10	$94.10
Purchase #4	$80.45	12.296%	$90.3421	$90.34	$90.35	$90.30
Purchase #5	$116.71	13.649%	$132.6397	$132.64	$132.65	$132.60
Purchase #6	$58.49	13.814%	$66.5698	$66.57	$66.55	$66.60
Purchase #7	$218.95	13.495%	$248.4973	$248.50	$248.50	$248.50
7 purchase totals =	$797.76		$887.8567	$887.86	$887.90	$887.80