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 $96.61   7.206%   $103.5717   $103.57   $103.55   $103.60  
  Purchase #2 $204.44   3.106%   $210.7899   $210.79   $210.80   $210.80  
  Purchase #3 $217.81   11.504%   $242.8669   $242.87   $242.85   $242.90  
  Purchase #4 $87.56   11.423%   $97.562   $97.56   $97.55   $97.60  
  Purchase #5 $147.91   8.322%   $160.2191   $160.22   $160.20   $160.20  
  Purchase #6 $173.39   8.405%   $187.9634   $187.96   $187.95   $188.00  
  Purchase #7 $249.76   6.847%   $266.8611   $266.86   $266.85   $266.90  
  7 purchase totals = $1,177.48       $1,269.8341   $1,269.83   $1,269.75   $1,270.00