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	$59.93	12.570%	$67.4632	$67.46	$67.45	$67.50
Purchase #2	$207.40	6.807%	$221.5177	$221.52	$221.50	$221.50
Purchase #3	$87.91	12.778%	$99.1431	$99.14	$99.15	$99.10
Purchase #4	$82.46	10.371%	$91.0119	$91.01	$91.00	$91.00
Purchase #5	$230.51	11.662%	$257.3921	$257.39	$257.40	$257.40
Purchase #6	$144.89	7.427%	$155.651	$155.65	$155.65	$155.70
Purchase #7	$51.78	5.554%	$54.6559	$54.66	$54.65	$54.70
7 purchase totals =	$864.88		$946.8349	$946.83	$946.80	$946.90