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 $182.46   7.314%   $195.8051   $195.81   $195.80   $195.80  
  Purchase #2 $155.95   11.838%   $174.4114   $174.41   $174.40   $174.40  
  Purchase #3 $230.56   6.501%   $245.5487   $245.55   $245.55   $245.50  
  Purchase #4 $51.29   10.151%   $56.4964   $56.50   $56.50   $56.50  
  Purchase #5 $196.81   7.393%   $211.3602   $211.36   $211.35   $211.40  
  Purchase #6 $238.47   11.104%   $264.9497   $264.95   $264.95   $264.90  
  Purchase #7 $204.58   4.854%   $214.5103   $214.51   $214.50   $214.50  
  7 purchase totals = $1,260.12       $1,363.0818   $1,363.09   $1,363.05   $1,363.00