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 $238.67   11.297%   $265.6325   $265.63   $265.65   $265.60  
  Purchase #2 $25.25   8.497%   $27.3955   $27.40   $27.40   $27.40  
  Purchase #3 $173.75   13.539%   $197.274   $197.27   $197.25   $197.30  
  Purchase #4 $31.84   11.472%   $35.4927   $35.49   $35.50   $35.50  
  Purchase #5 $217.80   11.771%   $243.4372   $243.44   $243.45   $243.40  
  Purchase #6 $153.95   6.332%   $163.6981   $163.70   $163.70   $163.70  
  Purchase #7 $187.48   5.391%   $197.587   $197.59   $197.60   $197.60  
  7 purchase totals = $1,028.74       $1,130.5170   $1,130.52   $1,130.55   $1,130.50