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 $32.25   11.208%   $35.8646   $35.86   $35.85   $35.90  
  Purchase #2 $141.35   10.234%   $155.8158   $155.82   $155.80   $155.80  
  Purchase #3 $93.58   11.868%   $104.6861   $104.69   $104.70   $104.70  
  Purchase #4 $235.89   6.127%   $250.343   $250.34   $250.35   $250.30  
  Purchase #5 $218.66   6.127%   $232.0573   $232.06   $232.05   $232.10  
  Purchase #6 $128.64   10.807%   $142.5421   $142.54   $142.55   $142.50  
  Purchase #7 $88.49   4.761%   $92.703   $92.70   $92.70   $92.70  
  7 purchase totals = $938.86       $1,014.0119   $1,014.01   $1,014.00   $1,014.00