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 $72.27   6.473%   $76.948   $76.95   $76.95   $76.90  
  Purchase #2 $239.52   11.134%   $266.1882   $266.19   $266.20   $266.20  
  Purchase #3 $222.28   12.152%   $249.2915   $249.29   $249.30   $249.30  
  Purchase #4 $20.26   8.225%   $21.9264   $21.93   $21.95   $21.90  
  Purchase #5 $34.65   10.552%   $38.3063   $38.31   $38.30   $38.30  
  Purchase #6 $20.57   11.641%   $22.9646   $22.96   $22.95   $23.00  
  Purchase #7 $159.92   10.647%   $176.9467   $176.95   $176.95   $176.90  
  7 purchase totals = $769.47       $852.5717   $852.58   $852.60   $852.50