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 $69.89   7.819%   $75.3547   $75.35   $75.35   $75.40  
  Purchase #2 $141.32   4.197%   $147.2512   $147.25   $147.25   $147.30  
  Purchase #3 $62.73   7.537%   $67.458   $67.46   $67.45   $67.50  
  Purchase #4 $204.49   8.358%   $221.5813   $221.58   $221.60   $221.60  
  Purchase #5 $225.75   6.863%   $241.2432   $241.24   $241.25   $241.20  
  Purchase #6 $249.42   6.236%   $264.9738   $264.97   $264.95   $265.00  
  Purchase #7 $208.84   4.265%   $217.747   $217.75   $217.75   $217.70  
  7 purchase totals = $1,162.44       $1,235.6092   $1,235.60   $1,235.60   $1,235.70