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	$144.70	9.454%	$158.3799	$158.38	$158.40	$158.40
Purchase #2	$86.91	12.345%	$97.639	$97.64	$97.65	$97.60
Purchase #3	$183.26	7.428%	$196.8726	$196.87	$196.85	$196.90
Purchase #4	$157.82	4.472%	$164.8777	$164.88	$164.90	$164.90
Purchase #5	$34.64	11.118%	$38.4913	$38.49	$38.50	$38.50
Purchase #6	$113.51	3.585%	$117.5793	$117.58	$117.60	$117.60
Purchase #7	$131.51	9.413%	$143.889	$143.89	$143.90	$143.90
7 purchase totals =	$852.35		$917.7288	$917.73	$917.80	$917.80