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 $23.26   6.299%   $24.7251   $24.73   $24.75   $24.70  
  Purchase #2 $146.31   5.264%   $154.0118   $154.01   $154.00   $154.00  
  Purchase #3 $170.63   8.809%   $185.6608   $185.66   $185.65   $185.70  
  Purchase #4 $215.78   8.229%   $233.5365   $233.54   $233.55   $233.50  
  Purchase #5 $179.64   6.471%   $191.2645   $191.26   $191.25   $191.30  
  Purchase #6 $120.95   3.372%   $125.0284   $125.03   $125.05   $125.00  
  Purchase #7 $247.51   8.423%   $268.3578   $268.36   $268.35   $268.40  
  7 purchase totals = $1,104.08       $1,182.5849   $1,182.59   $1,182.60   $1,182.60