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 $119.40   5.393%   $125.8392   $125.84   $125.85   $125.80  
  Purchase #2 $239.92   9.430%   $262.5445   $262.54   $262.55   $262.50  
  Purchase #3 $66.56   3.409%   $68.829   $68.83   $68.85   $68.80  
  Purchase #4 $60.59   6.160%   $64.3223   $64.32   $64.30   $64.30  
  Purchase #5 $193.58   9.167%   $211.3255   $211.33   $211.35   $211.30  
  Purchase #6 $242.36   11.635%   $270.5586   $270.56   $270.55   $270.60  
  Purchase #7 $86.47   13.527%   $98.1668   $98.17   $98.15   $98.20  
  7 purchase totals = $1,008.88       $1,101.5859   $1,101.59   $1,101.60   $1,101.50