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	$99.58	11.813%	$111.3434	$111.34	$111.35	$111.30
Purchase #2	$160.89	5.601%	$169.9014	$169.90	$169.90	$169.90
Purchase #3	$162.49	12.504%	$182.8077	$182.81	$182.80	$182.80
Purchase #4	$89.57	10.402%	$98.8871	$98.89	$98.90	$98.90
Purchase #5	$103.95	4.425%	$108.5498	$108.55	$108.55	$108.50
Purchase #6	$153.42	6.539%	$163.4521	$163.45	$163.45	$163.50
Purchase #7	$53.51	8.413%	$58.0118	$58.01	$58.00	$58.00
7 purchase totals =	$823.41		$892.9533	$892.95	$892.95	$892.90