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	$100.57	8.738%	$109.3578	$109.36	$109.35	$109.40
Purchase #2	$134.27	6.105%	$142.4672	$142.47	$142.45	$142.50
Purchase #3	$202.37	8.709%	$219.9944	$219.99	$220.00	$220.00
Purchase #4	$11.36	10.331%	$12.5336	$12.53	$12.55	$12.50
Purchase #5	$31.65	8.249%	$34.2608	$34.26	$34.25	$34.30
Purchase #6	$128.85	7.483%	$138.4918	$138.49	$138.50	$138.50
Purchase #7	$176.49	11.553%	$196.8799	$196.88	$196.90	$196.90
7 purchase totals =	$785.56		$853.9855	$853.98	$854.00	$854.10