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 $173.81   13.657%   $197.5472   $197.55   $197.55   $197.50  
  Purchase #2 $178.97   5.549%   $188.901   $188.90   $188.90   $188.90  
  Purchase #3 $32.59   5.162%   $34.2723   $34.27   $34.25   $34.30  
  Purchase #4 $187.49   12.757%   $211.4081   $211.41   $211.40   $211.40  
  Purchase #5 $178.96   7.588%   $192.5395   $192.54   $192.55   $192.50  
  Purchase #6 $135.60   12.555%   $152.6246   $152.62   $152.60   $152.60  
  Purchase #7 $186.40   5.777%   $197.1683   $197.17   $197.15   $197.20  
  7 purchase totals = $1,073.82       $1,174.4610   $1,174.46   $1,174.40   $1,174.40