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 $208.82   6.702%   $222.8151   $222.82   $222.80   $222.80  
  Purchase #2 $187.30   6.604%   $199.6693   $199.67   $199.65   $199.70  
  Purchase #3 $183.99   10.138%   $202.6429   $202.64   $202.65   $202.60  
  Purchase #4 $130.83   10.127%   $144.0792   $144.08   $144.10   $144.10  
  Purchase #5 $224.92   10.319%   $248.1295   $248.13   $248.15   $248.10  
  Purchase #6 $204.73   13.193%   $231.74   $231.74   $231.75   $231.70  
  Purchase #7 $201.73   7.497%   $216.8537   $216.85   $216.85   $216.90  
  7 purchase totals = $1,342.32       $1,465.9297   $1,465.93   $1,465.95   $1,465.90