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 $205.27   13.850%   $233.6999   $233.70   $233.70   $233.70  
  Purchase #2 $143.63   6.364%   $152.7706   $152.77   $152.75   $152.80  
  Purchase #3 $134.85   7.206%   $144.5673   $144.57   $144.55   $144.60  
  Purchase #4 $36.75   10.182%   $40.4919   $40.49   $40.50   $40.50  
  Purchase #5 $189.92   6.167%   $201.6324   $201.63   $201.65   $201.60  
  Purchase #6 $244.63   13.133%   $276.7573   $276.76   $276.75   $276.80  
  Purchase #7 $96.42   10.773%   $106.8073   $106.81   $106.80   $106.80  
  7 purchase totals = $1,051.47       $1,156.7267   $1,156.73   $1,156.70   $1,156.80