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 $192.89   8.839%   $209.9395   $209.94   $209.95   $209.90  
  Purchase #2 $137.63   6.560%   $146.6585   $146.66   $146.65   $146.70  
  Purchase #3 $187.30   13.697%   $212.9545   $212.95   $212.95   $213.00  
  Purchase #4 $196.58   4.214%   $204.8639   $204.86   $204.85   $204.90  
  Purchase #5 $57.96   4.192%   $60.3897   $60.39   $60.40   $60.40  
  Purchase #6 $69.67   13.624%   $79.1618   $79.16   $79.15   $79.20  
  Purchase #7 $163.83   10.444%   $180.9404   $180.94   $180.95   $180.90  
  7 purchase totals = $1,005.86       $1,094.9083   $1,094.90   $1,094.90   $1,095.00