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 $59.65   10.137%   $65.6967   $65.70   $65.70   $65.70  
  Purchase #2 $61.68   8.616%   $66.9943   $66.99   $67.00   $67.00  
  Purchase #3 $46.59   7.162%   $49.9268   $49.93   $49.95   $49.90  
  Purchase #4 $55.75   11.873%   $62.3692   $62.37   $62.35   $62.40  
  Purchase #5 $41.41   13.868%   $47.1527   $47.15   $47.15   $47.20  
  Purchase #6 $47.33   10.681%   $52.3853   $52.39   $52.40   $52.40  
  Purchase #7 $35.95   6.302%   $38.2156   $38.22   $38.20   $38.20  
  7 purchase totals = $348.36       $382.7406   $382.75   $382.75   $382.80