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	$100.85	13.797%	$114.7643	$114.76	$114.75	$114.80
Purchase #2	$119.40	10.115%	$131.4773	$131.48	$131.50	$131.50
Purchase #3	$211.53	12.449%	$237.8634	$237.86	$237.85	$237.90
Purchase #4	$133.83	13.203%	$151.4996	$151.50	$151.50	$151.50
Purchase #5	$196.52	8.821%	$213.855	$213.86	$213.85	$213.90
Purchase #6	$186.59	4.240%	$194.5014	$194.50	$194.50	$194.50
Purchase #7	$12.34	12.523%	$13.8853	$13.89	$13.90	$13.90
7 purchase totals =	$961.06		$1,057.8463	$1,057.85	$1,057.85	$1,058.00