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 $68.41   9.618%   $74.9897   $74.99   $75.00   $75.00  
  Purchase #2 $111.81   4.352%   $116.676   $116.68   $116.70   $116.70  
  Purchase #3 $7.67   6.482%   $8.1672   $8.17   $8.15   $8.20  
  Purchase #4 $65.42   3.755%   $67.8765   $67.88   $67.90   $67.90  
  Purchase #5 $171.67   4.324%   $179.093   $179.09   $179.10   $179.10  
  Purchase #6 $247.76   3.269%   $255.8593   $255.86   $255.85   $255.90  
  Purchase #7 $28.95   13.741%   $32.928   $32.93   $32.95   $32.90  
  7 purchase totals = $701.69       $735.5897   $735.60   $735.65   $735.70