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	$78.66	8.367%	$85.2415	$85.24	$85.25	$85.20
Purchase #2	$80.29	7.444%	$86.2668	$86.27	$86.25	$86.30
Purchase #3	$43.96	3.654%	$45.5663	$45.57	$45.55	$45.60
Purchase #4	$139.96	7.861%	$150.9623	$150.96	$150.95	$151.00
Purchase #5	$122.79	8.235%	$132.9018	$132.90	$132.90	$132.90
Purchase #6	$64.58	3.188%	$66.6388	$66.64	$66.65	$66.60
Purchase #7	$186.83	5.336%	$196.7992	$196.80	$196.80	$196.80
7 purchase totals =	$717.07		$764.3767	$764.38	$764.35	$764.40