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 $59.33   5.246%   $62.4425   $62.44   $62.45   $62.40  
  Purchase #2 $211.88   3.328%   $218.9314   $218.93   $218.95   $218.90  
  Purchase #3 $202.73   6.679%   $216.2703   $216.27   $216.25   $216.30  
  Purchase #4 $248.71   9.794%   $273.0687   $273.07   $273.05   $273.10  
  Purchase #5 $69.44   5.375%   $73.1724   $73.17   $73.15   $73.20  
  Purchase #6 $18.46   5.288%   $19.4362   $19.44   $19.45   $19.40  
  Purchase #7 $98.43   11.818%   $110.0625   $110.06   $110.05   $110.10  
  7 purchase totals = $908.98       $973.3840   $973.38   $973.35   $973.40