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 $119.97   11.666%   $133.9657   $133.97   $133.95   $134.00  
  Purchase #2 $184.45   7.454%   $198.1989   $198.20   $198.20   $198.20  
  Purchase #3 $188.26   7.131%   $201.6848   $201.68   $201.70   $201.70  
  Purchase #4 $200.62   4.445%   $209.5376   $209.54   $209.55   $209.50  
  Purchase #5 $227.36   8.641%   $247.0062   $247.01   $247.00   $247.00  
  Purchase #6 $170.64   9.768%   $187.3081   $187.31   $187.30   $187.30  
  Purchase #7 $168.50   9.361%   $184.2733   $184.27   $184.25   $184.30  
  7 purchase totals = $1,259.80       $1,361.9746   $1,361.98   $1,361.95   $1,362.00