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 $196.49   5.840%   $207.965   $207.97   $207.95   $208.00  
  Purchase #2 $241.50   13.435%   $273.9455   $273.95   $273.95   $273.90  
  Purchase #3 $13.98   4.362%   $14.5898   $14.59   $14.60   $14.60  
  Purchase #4 $203.45   6.599%   $216.8757   $216.88   $216.90   $216.90  
  Purchase #5 $75.57   13.467%   $85.747   $85.75   $85.75   $85.70  
  Purchase #6 $207.87   7.243%   $222.926   $222.93   $222.95   $222.90  
  Purchase #7 $186.57   12.267%   $209.4565   $209.46   $209.45   $209.50  
  7 purchase totals = $1,125.43       $1,231.5055   $1,231.53   $1,231.55   $1,231.50