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	$69.56	4.277%	$72.5351	$72.54	$72.55	$72.50
Purchase #2	$144.37	12.340%	$162.1853	$162.19	$162.20	$162.20
Purchase #3	$156.29	10.221%	$172.2644	$172.26	$172.25	$172.30
Purchase #4	$138.70	9.566%	$151.968	$151.97	$151.95	$152.00
Purchase #5	$124.79	5.763%	$131.9816	$131.98	$132.00	$132.00
Purchase #6	$127.90	9.858%	$140.5084	$140.51	$140.50	$140.50
Purchase #7	$86.80	6.501%	$92.4429	$92.44	$92.45	$92.40
7 purchase totals =	$848.41		$923.8857	$923.89	$923.90	$923.90