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 $65.75   5.353%   $69.2696   $69.27   $69.25   $69.30  
  Purchase #2 $220.98   6.798%   $236.0022   $236.00   $236.00   $236.00  
  Purchase #3 $192.33   7.620%   $206.9855   $206.99   $207.00   $207.00  
  Purchase #4 $33.42   6.406%   $35.5609   $35.56   $35.55   $35.60  
  Purchase #5 $228.33   6.641%   $243.4934   $243.49   $243.50   $243.50  
  Purchase #6 $125.55   12.872%   $141.7108   $141.71   $141.70   $141.70  
  Purchase #7 $235.88   6.829%   $251.9882   $251.99   $252.00   $252.00  
  7 purchase totals = $1,102.24       $1,185.0106   $1,185.01   $1,185.00   $1,185.10