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 $62.41   13.793%   $71.0182   $71.02   $71.00   $71.00  
  Purchase #2 $197.62   3.369%   $204.2778   $204.28   $204.30   $204.30  
  Purchase #3 $205.50   12.632%   $231.4588   $231.46   $231.45   $231.50  
  Purchase #4 $49.47   10.665%   $54.746   $54.75   $54.75   $54.70  
  Purchase #5 $36.47   7.594%   $39.2395   $39.24   $39.25   $39.20  
  Purchase #6 $186.82   3.543%   $193.439   $193.44   $193.45   $193.40  
  Purchase #7 $162.25   7.423%   $174.2938   $174.29   $174.30   $174.30  
  7 purchase totals = $900.54       $968.4731   $968.48   $968.50   $968.40