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 $89.89   9.702%   $98.6111   $98.61   $98.60   $98.60  
  Purchase #2 $194.27   12.537%   $218.6256   $218.63   $218.65   $218.60  
  Purchase #3 $241.73   10.522%   $267.1648   $267.16   $267.15   $267.20  
  Purchase #4 $165.61   5.134%   $174.1124   $174.11   $174.10   $174.10  
  Purchase #5 $216.53   13.792%   $246.3938   $246.39   $246.40   $246.40  
  Purchase #6 $225.81   11.544%   $251.8775   $251.88   $251.90   $251.90  
  Purchase #7 $204.77   7.229%   $219.5728   $219.57   $219.55   $219.60  
  7 purchase totals = $1,338.61       $1,476.3580   $1,476.35   $1,476.35   $1,476.40