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 $42.60   10.468%   $47.0594   $47.06   $47.05   $47.10  
  Purchase #2 $242.62   9.432%   $265.5039   $265.50   $265.50   $265.50  
  Purchase #3 $206.32   5.614%   $217.9028   $217.90   $217.90   $217.90  
  Purchase #4 $240.88   12.484%   $270.9515   $270.95   $270.95   $271.00  
  Purchase #5 $232.25   8.167%   $251.2179   $251.22   $251.20   $251.20  
  Purchase #6 $189.58   11.814%   $211.977   $211.98   $212.00   $212.00  
  Purchase #7 $159.27   9.730%   $174.767   $174.77   $174.75   $174.80  
  7 purchase totals = $1,313.52       $1,439.3795   $1,439.38   $1,439.35   $1,439.50