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 $175.28   6.465%   $186.6119   $186.61   $186.60   $186.60  
  Purchase #2 $47.58   5.582%   $50.2359   $50.24   $50.25   $50.20  
  Purchase #3 $171.53   3.309%   $177.2059   $177.21   $177.20   $177.20  
  Purchase #4 $146.95   11.768%   $164.2431   $164.24   $164.25   $164.20  
  Purchase #5 $108.29   3.724%   $112.3227   $112.32   $112.30   $112.30  
  Purchase #6 $204.62   4.561%   $213.9527   $213.95   $213.95   $214.00  
  Purchase #7 $152.87   5.574%   $161.391   $161.39   $161.40   $161.40  
  7 purchase totals = $1,007.12       $1,065.9632   $1,065.96   $1,065.95   $1,065.90