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 $80.33   6.655%   $85.676   $85.68   $85.70   $85.70  
  Purchase #2 $187.26   4.837%   $196.3178   $196.32   $196.30   $196.30  
  Purchase #3 $69.46   11.245%   $77.2708   $77.27   $77.25   $77.30  
  Purchase #4 $66.95   11.749%   $74.816   $74.82   $74.80   $74.80  
  Purchase #5 $205.69   3.684%   $213.2676   $213.27   $213.25   $213.30  
  Purchase #6 $36.67   8.206%   $39.6791   $39.68   $39.70   $39.70  
  Purchase #7 $48.42   3.752%   $50.2367   $50.24   $50.25   $50.20  
  7 purchase totals = $694.78       $737.2640   $737.28   $737.25   $737.30