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 $188.74   7.508%   $202.9106   $202.91   $202.90   $202.90  
  Purchase #2 $232.87   4.226%   $242.7111   $242.71   $242.70   $242.70  
  Purchase #3 $126.65   3.477%   $131.0536   $131.05   $131.05   $131.10  
  Purchase #4 $250.56   10.789%   $277.5929   $277.59   $277.60   $277.60  
  Purchase #5 $33.36   9.644%   $36.5772   $36.58   $36.60   $36.60  
  Purchase #6 $171.37   5.167%   $180.2247   $180.22   $180.20   $180.20  
  Purchase #7 $31.76   11.401%   $35.381   $35.38   $35.40   $35.40  
  7 purchase totals = $1,035.31       $1,106.4511   $1,106.44   $1,106.45   $1,106.50