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 $214.26   5.154%   $225.303   $225.30   $225.30   $225.30  
  Purchase #2 $238.91   12.868%   $269.6529   $269.65   $269.65   $269.70  
  Purchase #3 $138.75   3.518%   $143.6312   $143.63   $143.65   $143.60  
  Purchase #4 $206.94   4.484%   $216.2192   $216.22   $216.20   $216.20  
  Purchase #5 $27.95   8.686%   $30.3777   $30.38   $30.40   $30.40  
  Purchase #6 $143.57   4.388%   $149.8699   $149.87   $149.85   $149.90  
  Purchase #7 $24.68   5.696%   $26.0858   $26.09   $26.10   $26.10  
  7 purchase totals = $995.06       $1,061.1397   $1,061.14   $1,061.15   $1,061.20