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 $46.95   6.848%   $50.1651   $50.17   $50.15   $50.20  
  Purchase #2 $177.30   13.692%   $201.5759   $201.58   $201.60   $201.60  
  Purchase #3 $107.44   5.193%   $113.0194   $113.02   $113.00   $113.00  
  Purchase #4 $179.80   6.333%   $191.1867   $191.19   $191.20   $191.20  
  Purchase #5 $200.52   6.696%   $213.9468   $213.95   $213.95   $213.90  
  Purchase #6 $62.28   11.119%   $69.2049   $69.20   $69.20   $69.20  
  Purchase #7 $86.85   8.677%   $94.386   $94.39   $94.40   $94.40  
  7 purchase totals = $861.14       $933.4848   $933.50   $933.50   $933.50