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 $117.84   7.296%   $126.4376   $126.44   $126.45   $126.40  
  Purchase #2 $84.69   4.746%   $88.7094   $88.71   $88.70   $88.70  
  Purchase #3 $81.93   4.513%   $85.6275   $85.63   $85.65   $85.60  
  Purchase #4 $49.74   11.548%   $55.484   $55.48   $55.50   $55.50  
  Purchase #5 $202.80   11.872%   $226.8764   $226.88   $226.90   $226.90  
  Purchase #6 $209.35   9.436%   $229.1043   $229.10   $229.10   $229.10  
  Purchase #7 $227.74   11.313%   $253.5042   $253.50   $253.50   $253.50  
  7 purchase totals = $974.09       $1,065.7434   $1,065.74   $1,065.80   $1,065.70