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 $88.33   8.228%   $95.5978   $95.60   $95.60   $95.60  
  Purchase #2 $90.67   8.669%   $98.5302   $98.53   $98.55   $98.50  
  Purchase #3 $79.70   6.244%   $84.6765   $84.68   $84.70   $84.70  
  Purchase #4 $138.58   3.406%   $143.3   $143.30   $143.30   $143.30  
  Purchase #5 $19.38   4.147%   $20.1837   $20.18   $20.20   $20.20  
  Purchase #6 $55.91   5.360%   $58.9068   $58.91   $58.90   $58.90  
  Purchase #7 $93.77   11.112%   $104.1897   $104.19   $104.20   $104.20  
  7 purchase totals = $566.34       $605.3847   $605.39   $605.45   $605.40