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 $96.73   5.503%   $102.0531   $102.05   $102.05   $102.10  
  Purchase #2 $232.38   8.485%   $252.0974   $252.10   $252.10   $252.10  
  Purchase #3 $27.79   9.165%   $30.337   $30.34   $30.35   $30.30  
  Purchase #4 $146.60   10.294%   $161.691   $161.69   $161.70   $161.70  
  Purchase #5 $169.87   12.652%   $191.362   $191.36   $191.35   $191.40  
  Purchase #6 $205.57   3.378%   $212.5142   $212.51   $212.50   $212.50  
  Purchase #7 $209.27   3.704%   $217.0214   $217.02   $217.00   $217.00  
  7 purchase totals = $1,088.21       $1,167.0761   $1,167.07   $1,167.05   $1,167.10