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 $72.97   5.669%   $77.1067   $77.11   $77.10   $77.10  
  Purchase #2 $185.96   11.734%   $207.7805   $207.78   $207.80   $207.80  
  Purchase #3 $248.74   10.692%   $275.3353   $275.34   $275.35   $275.30  
  Purchase #4 $216.70   8.712%   $235.5789   $235.58   $235.60   $235.60  
  Purchase #5 $60.74   6.458%   $64.6626   $64.66   $64.65   $64.70  
  Purchase #6 $201.82   3.434%   $208.7505   $208.75   $208.75   $208.80  
  Purchase #7 $126.76   5.214%   $133.3693   $133.37   $133.35   $133.40  
  7 purchase totals = $1,113.69       $1,202.5838   $1,202.59   $1,202.60   $1,202.70