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 $93.45   11.543%   $104.2369   $104.24   $104.25   $104.20  
  Purchase #2 $32.91   11.264%   $36.617   $36.62   $36.60   $36.60  
  Purchase #3 $69.81   13.133%   $78.9781   $78.98   $79.00   $79.00  
  Purchase #4 $150.54   7.233%   $161.4286   $161.43   $161.45   $161.40  
  Purchase #5 $212.98   5.643%   $224.9985   $225.00   $225.00   $225.00  
  Purchase #6 $222.68   6.432%   $237.0028   $237.00   $237.00   $237.00  
  Purchase #7 $191.39   12.210%   $214.7587   $214.76   $214.75   $214.80  
  7 purchase totals = $973.76       $1,058.0206   $1,058.03   $1,058.05   $1,058.00