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	$63.90	13.308%	$72.4038	$72.40	$72.40	$72.40
Purchase #2	$59.55	13.256%	$67.4439	$67.44	$67.45	$67.40
Purchase #3	$11.78	13.378%	$13.3559	$13.36	$13.35	$13.40
Purchase #4	$246.96	3.870%	$256.5174	$256.52	$256.50	$256.50
Purchase #5	$175.76	4.633%	$183.903	$183.90	$183.90	$183.90
Purchase #6	$35.76	7.177%	$38.3265	$38.33	$38.35	$38.30
Purchase #7	$34.65	11.107%	$38.4986	$38.50	$38.50	$38.50
7 purchase totals =	$628.36		$670.4491	$670.45	$670.45	$670.40