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	$80.46	8.554%	$87.3425	$87.34	$87.35	$87.30
Purchase #2	$9.53	9.691%	$10.4536	$10.45	$10.45	$10.50
Purchase #3	$64.83	10.484%	$71.6268	$71.63	$71.65	$71.60
Purchase #4	$50.50	5.467%	$53.2608	$53.26	$53.25	$53.30
Purchase #5	$80.46	7.616%	$86.5878	$86.59	$86.60	$86.60
Purchase #6	$183.87	4.378%	$191.9198	$191.92	$191.90	$191.90
Purchase #7	$111.29	6.714%	$118.762	$118.76	$118.75	$118.80
7 purchase totals =	$580.94		$619.9533	$619.95	$619.95	$620.00