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 $67.26   13.158%   $76.1101   $76.11   $76.10   $76.10  
  Purchase #2 $196.26   11.421%   $218.6749   $218.67   $218.65   $218.70  
  Purchase #3 $48.33   3.198%   $49.8756   $49.88   $49.90   $49.90  
  Purchase #4 $16.50   13.364%   $18.7051   $18.71   $18.70   $18.70  
  Purchase #5 $114.89   8.872%   $125.083   $125.08   $125.10   $125.10  
  Purchase #6 $137.68   7.585%   $148.123   $148.12   $148.10   $148.10  
  Purchase #7 $115.49   8.709%   $125.548   $125.55   $125.55   $125.50  
  7 purchase totals = $696.41       $762.1197   $762.12   $762.10   $762.10