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 $33.69   7.210%   $36.119   $36.12   $36.10   $36.10  
  Purchase #2 $66.35   13.340%   $75.2011   $75.20   $75.20   $75.20  
  Purchase #3 $104.42   12.299%   $117.2626   $117.26   $117.25   $117.30  
  Purchase #4 $22.41   9.841%   $24.6154   $24.62   $24.60   $24.60  
  Purchase #5 $125.93   4.253%   $131.2858   $131.29   $131.30   $131.30  
  Purchase #6 $204.56   4.681%   $214.1355   $214.14   $214.15   $214.10  
  Purchase #7 $207.82   12.527%   $233.8536   $233.85   $233.85   $233.90  
  7 purchase totals = $765.18       $832.4730   $832.48   $832.45   $832.50