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 $183.37   10.133%   $201.9509   $201.95   $201.95   $202.00  
  Purchase #2 $51.67   3.714%   $53.589   $53.59   $53.60   $53.60  
  Purchase #3 $129.67   5.153%   $136.3519   $136.35   $136.35   $136.40  
  Purchase #4 $180.38   12.305%   $202.5758   $202.58   $202.60   $202.60  
  Purchase #5 $130.36   8.588%   $141.5553   $141.56   $141.55   $141.60  
  Purchase #6 $49.60   6.400%   $52.7744   $52.77   $52.75   $52.80  
  Purchase #7 $89.76   4.110%   $93.4491   $93.45   $93.45   $93.40  
  7 purchase totals = $814.81       $882.2464   $882.25   $882.25   $882.40