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 $235.26   11.394%   $262.0655   $262.07   $262.05   $262.10  
  Purchase #2 $35.44   9.142%   $38.6799   $38.68   $38.70   $38.70  
  Purchase #3 $175.67   4.386%   $183.3749   $183.37   $183.35   $183.40  
  Purchase #4 $182.78   12.574%   $205.7628   $205.76   $205.75   $205.80  
  Purchase #5 $53.60   12.293%   $60.189   $60.19   $60.20   $60.20  
  Purchase #6 $66.93   13.303%   $75.8337   $75.83   $75.85   $75.80  
  Purchase #7 $116.85   7.828%   $125.997   $126.00   $126.00   $126.00  
  7 purchase totals = $866.53       $951.9028   $951.90   $951.90   $952.00