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 $89.40   6.212%   $94.9535   $94.95   $94.95   $95.00  
  Purchase #2 $82.83   11.322%   $92.208   $92.21   $92.20   $92.20  
  Purchase #3 $155.73   4.199%   $162.2691   $162.27   $162.25   $162.30  
  Purchase #4 $107.34   6.184%   $113.9779   $113.98   $114.00   $114.00  
  Purchase #5 $123.95   8.374%   $134.3296   $134.33   $134.35   $134.30  
  Purchase #6 $89.40   3.649%   $92.6622   $92.66   $92.65   $92.70  
  Purchase #7 $38.70   12.279%   $43.452   $43.45   $43.45   $43.50  
  7 purchase totals = $687.35       $733.8523   $733.85   $733.85   $734.00