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 $188.53   3.691%   $195.4886   $195.49   $195.50   $195.50  
  Purchase #2 $98.85   7.373%   $106.1382   $106.14   $106.15   $106.10  
  Purchase #3 $243.65   7.287%   $261.4048   $261.40   $261.40   $261.40  
  Purchase #4 $47.73   3.339%   $49.3237   $49.32   $49.30   $49.30  
  Purchase #5 $177.75   12.867%   $200.6211   $200.62   $200.60   $200.60  
  Purchase #6 $61.33   3.502%   $63.4778   $63.48   $63.50   $63.50  
  Purchase #7 $206.67   13.494%   $234.558   $234.56   $234.55   $234.60  
  7 purchase totals = $1,024.51       $1,111.0122   $1,111.01   $1,111.00   $1,111.00