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 $177.33   9.657%   $194.4548   $194.45   $194.45   $194.50  
  Purchase #2 $84.57   11.723%   $94.4841   $94.48   $94.50   $94.50  
  Purchase #3 $137.62   13.659%   $156.4175   $156.42   $156.40   $156.40  
  Purchase #4 $107.91   8.651%   $117.2453   $117.25   $117.25   $117.20  
  Purchase #5 $198.47   3.667%   $205.7479   $205.75   $205.75   $205.70  
  Purchase #6 $58.60   5.364%   $61.7433   $61.74   $61.75   $61.70  
  Purchase #7 $181.57   6.546%   $193.4556   $193.46   $193.45   $193.50  
  7 purchase totals = $946.07       $1,023.5485   $1,023.55   $1,023.55   $1,023.50