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 $69.26   11.577%   $77.2782   $77.28   $77.30   $77.30  
  Purchase #2 $114.60   10.640%   $126.7934   $126.79   $126.80   $126.80  
  Purchase #3 $51.60   8.583%   $56.0288   $56.03   $56.05   $56.00  
  Purchase #4 $188.44   12.529%   $212.0496   $212.05   $212.05   $212.00  
  Purchase #5 $189.67   7.577%   $204.0413   $204.04   $204.05   $204.00  
  Purchase #6 $222.42   12.265%   $249.6998   $249.70   $249.70   $249.70  
  Purchase #7 $249.31   11.663%   $278.387   $278.39   $278.40   $278.40  
  7 purchase totals = $1,085.30       $1,204.2781   $1,204.28   $1,204.35   $1,204.20