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 $193.26   6.209%   $205.2595   $205.26   $205.25   $205.30  
  Purchase #2 $194.89   5.301%   $205.2211   $205.22   $205.20   $205.20  
  Purchase #3 $16.90   5.254%   $17.7879   $17.79   $17.80   $17.80  
  Purchase #4 $32.90   8.800%   $35.7952   $35.80   $35.80   $35.80  
  Purchase #5 $160.57   3.625%   $166.3907   $166.39   $166.40   $166.40  
  Purchase #6 $175.68   11.594%   $196.0483   $196.05   $196.05   $196.00  
  Purchase #7 $171.38   8.634%   $186.1769   $186.18   $186.20   $186.20  
  7 purchase totals = $945.58       $1,012.6796   $1,012.69   $1,012.70   $1,012.70