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 $46.97   6.865%   $50.1945   $50.19   $50.20   $50.20  
  Purchase #2 $141.29   7.366%   $151.6974   $151.70   $151.70   $151.70  
  Purchase #3 $236.74   11.823%   $264.7298   $264.73   $264.75   $264.70  
  Purchase #4 $28.29   11.499%   $31.5431   $31.54   $31.55   $31.50  
  Purchase #5 $61.56   8.357%   $66.7046   $66.70   $66.70   $66.70  
  Purchase #6 $207.56   9.656%   $227.602   $227.60   $227.60   $227.60  
  Purchase #7 $206.89   9.596%   $226.7432   $226.74   $226.75   $226.70  
  7 purchase totals = $929.30       $1,019.2146   $1,019.20   $1,019.25   $1,019.10