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 $231.61   13.575%   $263.0511   $263.05   $263.05   $263.10  
  Purchase #2 $34.70   6.392%   $36.918   $36.92   $36.90   $36.90  
  Purchase #3 $149.74   4.218%   $156.056   $156.06   $156.05   $156.10  
  Purchase #4 $177.88   10.306%   $196.2123   $196.21   $196.20   $196.20  
  Purchase #5 $241.39   8.772%   $262.5647   $262.56   $262.55   $262.60  
  Purchase #6 $37.57   13.524%   $42.651   $42.65   $42.65   $42.70  
  Purchase #7 $218.98   8.658%   $237.9393   $237.94   $237.95   $237.90  
  7 purchase totals = $1,091.87       $1,195.3924   $1,195.39   $1,195.35   $1,195.50