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 $85.56   12.274%   $96.0616   $96.06   $96.05   $96.10  
  Purchase #2 $175.56   12.493%   $197.4927   $197.49   $197.50   $197.50  
  Purchase #3 $201.92   5.192%   $212.4037   $212.40   $212.40   $212.40  
  Purchase #4 $223.85   9.636%   $245.4202   $245.42   $245.40   $245.40  
  Purchase #5 $135.71   7.320%   $145.644   $145.64   $145.65   $145.60  
  Purchase #6 $134.65   4.662%   $140.9274   $140.93   $140.95   $140.90  
  Purchase #7 $161.39   4.621%   $168.8478   $168.85   $168.85   $168.80  
  7 purchase totals = $1,118.64       $1,206.7974   $1,206.79   $1,206.80   $1,206.70