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 $64.82   8.811%   $70.5313   $70.53   $70.55   $70.50  
  Purchase #2 $208.83   10.856%   $231.5006   $231.50   $231.50   $231.50  
  Purchase #3 $98.61   8.479%   $106.9711   $106.97   $106.95   $107.00  
  Purchase #4 $249.40   6.131%   $264.6907   $264.69   $264.70   $264.70  
  Purchase #5 $201.34   5.482%   $212.3775   $212.38   $212.40   $212.40  
  Purchase #6 $230.47   9.650%   $252.7104   $252.71   $252.70   $252.70  
  Purchase #7 $215.39   4.623%   $225.3475   $225.35   $225.35   $225.30  
  7 purchase totals = $1,268.86       $1,364.1291   $1,364.13   $1,364.15   $1,364.10