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 $88.48   10.311%   $97.6032   $97.60   $97.60   $97.60  
  Purchase #2 $121.95   5.131%   $128.2073   $128.21   $128.20   $128.20  
  Purchase #3 $102.38   10.244%   $112.8678   $112.87   $112.85   $112.90  
  Purchase #4 $231.35   13.321%   $262.1681   $262.17   $262.15   $262.20  
  Purchase #5 $215.72   9.701%   $236.647   $236.65   $236.65   $236.60  
  Purchase #6 $111.36   12.460%   $125.2355   $125.24   $125.25   $125.20  
  Purchase #7 $230.97   9.147%   $252.0968   $252.10   $252.10   $252.10  
  7 purchase totals = $1,102.21       $1,214.8257   $1,214.84   $1,214.80   $1,214.80