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 $82.56   12.330%   $92.7396   $92.74   $92.75   $92.70  
  Purchase #2 $120.54   3.732%   $125.0386   $125.04   $125.05   $125.00  
  Purchase #3 $193.68   7.515%   $208.2351   $208.24   $208.25   $208.20  
  Purchase #4 $199.53   11.165%   $221.8075   $221.81   $221.80   $221.80  
  Purchase #5 $200.76   3.665%   $208.1179   $208.12   $208.10   $208.10  
  Purchase #6 $167.72   6.376%   $178.4138   $178.41   $178.40   $178.40  
  Purchase #7 $8.42   11.566%   $9.3939   $9.39   $9.40   $9.40  
  7 purchase totals = $973.21       $1,043.7464   $1,043.75   $1,043.75   $1,043.60