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 $88.98   7.340%   $95.5111   $95.51   $95.50   $95.50  
  Purchase #2 $148.37   13.770%   $168.8005   $168.80   $168.80   $168.80  
  Purchase #3 $219.96   9.327%   $240.4757   $240.48   $240.50   $240.50  
  Purchase #4 $29.50   13.277%   $33.4167   $33.42   $33.40   $33.40  
  Purchase #5 $178.39   8.193%   $193.0055   $193.01   $193.00   $193.00  
  Purchase #6 $38.66   10.324%   $42.6513   $42.65   $42.65   $42.70  
  Purchase #7 $165.29   5.684%   $174.6851   $174.69   $174.70   $174.70  
  7 purchase totals = $869.15       $948.5459   $948.56   $948.55   $948.60