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 $41.33   11.362%   $46.0259   $46.03   $46.05   $46.00  
  Purchase #2 $237.26   11.483%   $264.5046   $264.50   $264.50   $264.50  
  Purchase #3 $95.50   12.256%   $107.2045   $107.20   $107.20   $107.20  
  Purchase #4 $22.37   4.793%   $23.4422   $23.44   $23.45   $23.40  
  Purchase #5 $58.60   13.204%   $66.3375   $66.34   $66.35   $66.30  
  Purchase #6 $35.97   6.576%   $38.3354   $38.34   $38.35   $38.30  
  Purchase #7 $201.55   3.445%   $208.4934   $208.49   $208.50   $208.50  
  7 purchase totals = $692.58       $754.3435   $754.34   $754.40   $754.20