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 $60.72   7.687%   $65.3875   $65.39   $65.40   $65.40  
  Purchase #2 $245.68   3.109%   $253.3182   $253.32   $253.30   $253.30  
  Purchase #3 $119.49   10.746%   $132.3304   $132.33   $132.35   $132.30  
  Purchase #4 $192.79   3.138%   $198.8398   $198.84   $198.85   $198.80  
  Purchase #5 $53.58   7.609%   $57.6569   $57.66   $57.65   $57.70  
  Purchase #6 $228.51   3.433%   $236.3547   $236.35   $236.35   $236.40  
  Purchase #7 $190.37   9.649%   $208.7388   $208.74   $208.75   $208.70  
  7 purchase totals = $1,091.14       $1,152.6263   $1,152.63   $1,152.65   $1,152.60