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 $58.75   5.873%   $62.2004   $62.20   $62.20   $62.20  
  Purchase #2 $61.79   4.747%   $64.7232   $64.72   $64.70   $64.70  
  Purchase #3 $209.98   10.134%   $231.2594   $231.26   $231.25   $231.30  
  Purchase #4 $188.64   6.836%   $201.5354   $201.54   $201.55   $201.50  
  Purchase #5 $78.72   13.791%   $89.5763   $89.58   $89.60   $89.60  
  Purchase #6 $143.90   8.364%   $155.9358   $155.94   $155.95   $155.90  
  Purchase #7 $238.94   5.815%   $252.8344   $252.83   $252.85   $252.80  
  7 purchase totals = $980.72       $1,058.0649   $1,058.07   $1,058.10   $1,058.00