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 $230.25   13.810%   $262.0475   $262.05   $262.05   $262.00  
  Purchase #2 $168.71   3.496%   $174.6081   $174.61   $174.60   $174.60  
  Purchase #3 $207.91   8.809%   $226.2248   $226.22   $226.20   $226.20  
  Purchase #4 $222.74   12.391%   $250.3397   $250.34   $250.35   $250.30  
  Purchase #5 $134.72   12.634%   $151.7405   $151.74   $151.75   $151.70  
  Purchase #6 $55.41   8.557%   $60.1514   $60.15   $60.15   $60.20  
  Purchase #7 $217.70   6.118%   $231.0189   $231.02   $231.00   $231.00  
  7 purchase totals = $1,237.44       $1,356.1309   $1,356.13   $1,356.10   $1,356.00