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 $191.81   13.472%   $217.6506   $217.65   $217.65   $217.70  
  Purchase #2 $38.39   8.601%   $41.6919   $41.69   $41.70   $41.70  
  Purchase #3 $84.63   8.870%   $92.1367   $92.14   $92.15   $92.10  
  Purchase #4 $205.74   11.591%   $229.5873   $229.59   $229.60   $229.60  
  Purchase #5 $60.94   4.501%   $63.6829   $63.68   $63.70   $63.70  
  Purchase #6 $216.75   5.360%   $228.3678   $228.37   $228.35   $228.40  
  Purchase #7 $157.43   13.118%   $178.0817   $178.08   $178.10   $178.10  
  7 purchase totals = $955.69       $1,051.1989   $1,051.20   $1,051.25   $1,051.30