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 $233.99   3.322%   $241.7631   $241.76   $241.75   $241.80  
  Purchase #2 $230.76   13.283%   $261.4119   $261.41   $261.40   $261.40  
  Purchase #3 $165.30   5.712%   $174.7419   $174.74   $174.75   $174.70  
  Purchase #4 $81.91   12.864%   $92.4469   $92.45   $92.45   $92.40  
  Purchase #5 $18.58   9.753%   $20.3921   $20.39   $20.40   $20.40  
  Purchase #6 $101.89   3.833%   $105.7954   $105.80   $105.80   $105.80  
  Purchase #7 $186.77   6.148%   $198.2526   $198.25   $198.25   $198.30  
  7 purchase totals = $1,019.20       $1,094.8039   $1,094.80   $1,094.80   $1,094.80