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	$169.86	8.826%	$184.8518	$184.85	$184.85	$184.90
Purchase #2	$36.89	7.456%	$39.6405	$39.64	$39.65	$39.60
Purchase #3	$47.78	4.375%	$49.8704	$49.87	$49.85	$49.90
Purchase #4	$123.76	11.204%	$137.6261	$137.63	$137.65	$137.60
Purchase #5	$89.59	9.520%	$98.119	$98.12	$98.10	$98.10
Purchase #6	$157.51	3.400%	$162.8653	$162.87	$162.85	$162.90
Purchase #7	$195.59	13.766%	$222.5149	$222.51	$222.50	$222.50
7 purchase totals =	$820.98		$895.4880	$895.49	$895.45	$895.50