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 $191.39   8.664%   $207.972   $207.97   $207.95   $208.00  
  Purchase #2 $33.58   7.273%   $36.0223   $36.02   $36.00   $36.00  
  Purchase #3 $249.73   4.349%   $260.5908   $260.59   $260.60   $260.60  
  Purchase #4 $76.97   4.102%   $80.1273   $80.13   $80.15   $80.10  
  Purchase #5 $233.87   5.355%   $246.3937   $246.39   $246.40   $246.40  
  Purchase #6 $7.33   9.262%   $8.0089   $8.01   $8.00   $8.00  
  Purchase #7 $170.79   9.276%   $186.6325   $186.63   $186.65   $186.60  
  7 purchase totals = $963.66       $1,025.7475   $1,025.74   $1,025.75   $1,025.70