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	$153.48	9.491%	$168.0468	$168.05	$168.05	$168.00
Purchase #2	$217.78	6.343%	$231.5938	$231.59	$231.60	$231.60
Purchase #3	$250.96	4.443%	$262.1102	$262.11	$262.10	$262.10
Purchase #4	$64.27	5.314%	$67.6853	$67.69	$67.70	$67.70
Purchase #5	$50.33	4.852%	$52.772	$52.77	$52.75	$52.80
Purchase #6	$94.70	8.340%	$102.598	$102.60	$102.60	$102.60
Purchase #7	$31.73	3.210%	$32.7485	$32.75	$32.75	$32.70
7 purchase totals =	$863.25		$917.5546	$917.56	$917.55	$917.50