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 $125.75   12.698%   $141.7177   $141.72   $141.70   $141.70  
  Purchase #2 $131.36   3.165%   $135.5175   $135.52   $135.50   $135.50  
  Purchase #3 $66.66   4.814%   $69.869   $69.87   $69.85   $69.90  
  Purchase #4 $113.46   9.581%   $124.3306   $124.33   $124.35   $124.30  
  Purchase #5 $184.57   6.580%   $196.7147   $196.71   $196.70   $196.70  
  Purchase #6 $200.95   8.616%   $218.2639   $218.26   $218.25   $218.30  
  Purchase #7 $127.38   8.242%   $137.8787   $137.88   $137.90   $137.90  
  7 purchase totals = $950.13       $1,024.2921   $1,024.29   $1,024.25   $1,024.30