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 $76.38   12.165%   $85.6716   $85.67   $85.65   $85.70  
  Purchase #2 $187.68   12.268%   $210.7046   $210.70   $210.70   $210.70  
  Purchase #3 $93.29   9.299%   $101.965   $101.97   $101.95   $102.00  
  Purchase #4 $242.40   12.473%   $272.6346   $272.63   $272.65   $272.60  
  Purchase #5 $23.72   5.414%   $25.0042   $25.00   $25.00   $25.00  
  Purchase #6 $227.33   4.607%   $237.8031   $237.80   $237.80   $237.80  
  Purchase #7 $70.59   8.658%   $76.7017   $76.70   $76.70   $76.70  
  7 purchase totals = $921.39       $1,010.4848   $1,010.47   $1,010.45   $1,010.50