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 $63.53   11.682%   $70.9516   $70.95   $70.95   $71.00  
  Purchase #2 $215.38   6.264%   $228.8714   $228.87   $228.85   $228.90  
  Purchase #3 $213.96   10.659%   $236.766   $236.77   $236.75   $236.80  
  Purchase #4 $113.71   3.390%   $117.5648   $117.56   $117.55   $117.60  
  Purchase #5 $203.55   4.486%   $212.6813   $212.68   $212.70   $212.70  
  Purchase #6 $119.66   5.800%   $126.6003   $126.60   $126.60   $126.60  
  Purchase #7 $203.28   8.757%   $221.0812   $221.08   $221.10   $221.10  
  7 purchase totals = $1,133.07       $1,214.5166   $1,214.51   $1,214.50   $1,214.70