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 $84.98   11.842%   $95.0433   $95.04   $95.05   $95.00  
  Purchase #2 $250.60   8.409%   $271.673   $271.67   $271.65   $271.70  
  Purchase #3 $177.55   13.620%   $201.7323   $201.73   $201.75   $201.70  
  Purchase #4 $72.34   11.512%   $80.6678   $80.67   $80.65   $80.70  
  Purchase #5 $19.37   6.811%   $20.6893   $20.69   $20.70   $20.70  
  Purchase #6 $14.92   4.768%   $15.6314   $15.63   $15.65   $15.60  
  Purchase #7 $19.54   4.641%   $20.4469   $20.45   $20.45   $20.40  
  7 purchase totals = $639.30       $705.8840   $705.88   $705.90   $705.80