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 $101.88   12.543%   $114.6588   $114.66   $114.65   $114.70  
  Purchase #2 $240.28   9.619%   $263.3925   $263.39   $263.40   $263.40  
  Purchase #3 $202.60   8.268%   $219.351   $219.35   $219.35   $219.40  
  Purchase #4 $223.43   11.719%   $249.6138   $249.61   $249.60   $249.60  
  Purchase #5 $53.73   12.506%   $60.4495   $60.45   $60.45   $60.40  
  Purchase #6 $29.94   5.346%   $31.5406   $31.54   $31.55   $31.50  
  Purchase #7 $245.51   4.705%   $257.0612   $257.06   $257.05   $257.10  
  7 purchase totals = $1,097.37       $1,196.0674   $1,196.06   $1,196.05   $1,196.10