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 $208.40   9.285%   $227.7499   $227.75   $227.75   $227.70  
  Purchase #2 $175.86   3.333%   $181.7214   $181.72   $181.70   $181.70  
  Purchase #3 $29.40   9.216%   $32.1095   $32.11   $32.10   $32.10  
  Purchase #4 $245.51   4.188%   $255.792   $255.79   $255.80   $255.80  
  Purchase #5 $26.55   11.734%   $29.6654   $29.67   $29.65   $29.70  
  Purchase #6 $190.36   3.737%   $197.4738   $197.47   $197.45   $197.50  
  Purchase #7 $198.98   4.485%   $207.9043   $207.90   $207.90   $207.90  
  7 purchase totals = $1,075.06       $1,132.4163   $1,132.41   $1,132.35   $1,132.40