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 $40.41   8.793%   $43.9633   $43.96   $43.95   $44.00  
  Purchase #2 $250.83   6.498%   $267.1289   $267.13   $267.15   $267.10  
  Purchase #3 $49.84   8.329%   $53.9912   $53.99   $54.00   $54.00  
  Purchase #4 $249.33   6.255%   $264.9256   $264.93   $264.95   $264.90  
  Purchase #5 $41.95   13.769%   $47.7261   $47.73   $47.75   $47.70  
  Purchase #6 $182.90   12.827%   $206.3606   $206.36   $206.35   $206.40  
  Purchase #7 $220.43   6.753%   $235.3156   $235.32   $235.30   $235.30  
  7 purchase totals = $1,035.69       $1,119.4113   $1,119.42   $1,119.45   $1,119.40