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	$199.37	11.108%	$221.516	$221.52	$221.50	$221.50
Purchase #2	$142.33	7.853%	$153.5072	$153.51	$153.50	$153.50
Purchase #3	$54.61	13.524%	$61.9955	$62.00	$62.00	$62.00
Purchase #4	$150.77	4.735%	$157.909	$157.91	$157.90	$157.90
Purchase #5	$95.43	5.725%	$100.8934	$100.89	$100.90	$100.90
Purchase #6	$67.83	12.531%	$76.3298	$76.33	$76.35	$76.30
Purchase #7	$36.79	10.863%	$40.7865	$40.79	$40.80	$40.80
7 purchase totals =	$747.13		$812.9374	$812.95	$812.95	$812.90