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 $34.70   4.524%   $36.2698   $36.27   $36.25   $36.30  
  Purchase #2 $182.87   4.642%   $191.3588   $191.36   $191.35   $191.40  
  Purchase #3 $227.87   9.569%   $249.6749   $249.67   $249.65   $249.70  
  Purchase #4 $211.53   8.449%   $229.4022   $229.40   $229.40   $229.40  
  Purchase #5 $35.51   10.544%   $39.2542   $39.25   $39.25   $39.30  
  Purchase #6 $105.68   6.311%   $112.3495   $112.35   $112.35   $112.30  
  Purchase #7 $197.34   10.844%   $218.7395   $218.74   $218.75   $218.70  
  7 purchase totals = $995.50       $1,077.0489   $1,077.04   $1,077.00   $1,077.10