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 $193.27   6.775%   $206.364   $206.36   $206.35   $206.40  
  Purchase #2 $112.62   4.389%   $117.5629   $117.56   $117.55   $117.60  
  Purchase #3 $196.43   12.679%   $221.3354   $221.34   $221.35   $221.30  
  Purchase #4 $173.72   4.427%   $181.4106   $181.41   $181.40   $181.40  
  Purchase #5 $119.93   11.229%   $133.3969   $133.40   $133.40   $133.40  
  Purchase #6 $139.90   10.261%   $154.2551   $154.26   $154.25   $154.30  
  Purchase #7 $36.93   3.663%   $38.2827   $38.28   $38.30   $38.30  
  7 purchase totals = $972.80       $1,052.6076   $1,052.61   $1,052.60   $1,052.70