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	$109.30	3.226%	$112.826	$112.83	$112.85	$112.80
Purchase #2	$190.39	3.363%	$196.7928	$196.79	$196.80	$196.80
Purchase #3	$36.90	12.706%	$41.5885	$41.59	$41.60	$41.60
Purchase #4	$126.92	7.517%	$136.4606	$136.46	$136.45	$136.50
Purchase #5	$87.99	12.826%	$99.2756	$99.28	$99.30	$99.30
Purchase #6	$71.35	8.484%	$77.4033	$77.40	$77.40	$77.40
Purchase #7	$227.60	10.692%	$251.935	$251.94	$251.95	$251.90
7 purchase totals =	$850.45		$916.2818	$916.29	$916.35	$916.30