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 $61.49   5.431%   $64.8295   $64.83   $64.85   $64.80  
  Purchase #2 $114.40   8.379%   $123.9856   $123.99   $124.00   $124.00  
  Purchase #3 $93.84   6.243%   $99.6984   $99.70   $99.70   $99.70  
  Purchase #4 $94.57   13.120%   $106.9776   $106.98   $107.00   $107.00  
  Purchase #5 $242.74   4.439%   $253.5152   $253.52   $253.50   $253.50  
  Purchase #6 $40.61   13.158%   $45.9535   $45.95   $45.95   $46.00  
  Purchase #7 $58.55   13.760%   $66.6065   $66.61   $66.60   $66.60  
  7 purchase totals = $706.20       $761.5663   $761.58   $761.60   $761.60