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 $232.94   5.586%   $245.952   $245.95   $245.95   $246.00  
  Purchase #2 $110.30   3.629%   $114.3028   $114.30   $114.30   $114.30  
  Purchase #3 $146.71   10.386%   $161.9473   $161.95   $161.95   $161.90  
  Purchase #4 $139.42   10.866%   $154.5694   $154.57   $154.55   $154.60  
  Purchase #5 $58.32   6.226%   $61.951   $61.95   $61.95   $62.00  
  Purchase #6 $191.56   7.474%   $205.8772   $205.88   $205.90   $205.90  
  Purchase #7 $157.75   8.282%   $170.8149   $170.81   $170.80   $170.80  
  7 purchase totals = $1,037.00       $1,115.4146   $1,115.41   $1,115.40   $1,115.50