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	$103.87	5.434%	$109.5143	$109.51	$109.50	$109.50
Purchase #2	$8.95	7.130%	$9.5881	$9.59	$9.60	$9.60
Purchase #3	$182.65	10.498%	$201.8246	$201.82	$201.80	$201.80
Purchase #4	$72.82	7.402%	$78.2101	$78.21	$78.20	$78.20
Purchase #5	$212.56	5.792%	$224.8715	$224.87	$224.85	$224.90
Purchase #6	$84.34	7.558%	$90.7144	$90.71	$90.70	$90.70
Purchase #7	$65.88	9.847%	$72.3672	$72.37	$72.35	$72.40
7 purchase totals =	$731.07		$787.0902	$787.08	$787.00	$787.10