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 $118.45   5.866%   $125.3983   $125.40   $125.40   $125.40  
  Purchase #2 $167.95   12.332%   $188.6616   $188.66   $188.65   $188.70  
  Purchase #3 $90.94   12.344%   $102.1656   $102.17   $102.15   $102.20  
  Purchase #4 $86.36   6.527%   $91.9967   $92.00   $92.00   $92.00  
  Purchase #5 $78.93   13.408%   $89.5129   $89.51   $89.50   $89.50  
  Purchase #6 $199.50   6.578%   $212.6231   $212.62   $212.60   $212.60  
  Purchase #7 $200.28   10.541%   $221.3915   $221.39   $221.40   $221.40  
  7 purchase totals = $942.41       $1,031.7497   $1,031.75   $1,031.70   $1,031.80