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 $188.66   3.691%   $195.6234   $195.62   $195.60   $195.60  
  Purchase #2 $146.60   10.149%   $161.4784   $161.48   $161.50   $161.50  
  Purchase #3 $18.54   12.325%   $20.8251   $20.83   $20.85   $20.80  
  Purchase #4 $28.39   11.751%   $31.7261   $31.73   $31.75   $31.70  
  Purchase #5 $168.74   6.783%   $180.1856   $180.19   $180.20   $180.20  
  Purchase #6 $19.49   11.125%   $21.6583   $21.66   $21.65   $21.70  
  Purchase #7 $131.27   12.300%   $147.4162   $147.42   $147.40   $147.40  
  7 purchase totals = $701.69       $758.9131   $758.93   $758.95   $758.90