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 $67.52   11.826%   $75.5049   $75.50   $75.50   $75.50  
  Purchase #2 $220.87   7.357%   $237.1194   $237.12   $237.10   $237.10  
  Purchase #3 $107.88   10.856%   $119.5915   $119.59   $119.60   $119.60  
  Purchase #4 $172.76   12.606%   $194.5381   $194.54   $194.55   $194.50  
  Purchase #5 $192.56   12.801%   $217.2096   $217.21   $217.20   $217.20  
  Purchase #6 $117.27   4.571%   $122.6304   $122.63   $122.65   $122.60  
  Purchase #7 $84.60   6.264%   $89.8993   $89.90   $89.90   $89.90  
  7 purchase totals = $963.46       $1,056.4932   $1,056.49   $1,056.50   $1,056.40