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 $87.74   8.275%   $95.0005   $95.00   $95.00   $95.00  
  Purchase #2 $114.33   4.269%   $119.2107   $119.21   $119.20   $119.20  
  Purchase #3 $210.33   9.551%   $230.4186   $230.42   $230.40   $230.40  
  Purchase #4 $172.95   4.650%   $180.9922   $180.99   $181.00   $181.00  
  Purchase #5 $46.33   13.484%   $52.5771   $52.58   $52.60   $52.60  
  Purchase #6 $236.74   8.771%   $257.5045   $257.50   $257.50   $257.50  
  Purchase #7 $59.36   11.503%   $66.1882   $66.19   $66.20   $66.20  
  7 purchase totals = $927.78       $1,001.8918   $1,001.89   $1,001.90   $1,001.90