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 $230.82   6.852%   $246.6358   $246.64   $246.65   $246.60  
  Purchase #2 $194.55   6.835%   $207.8475   $207.85   $207.85   $207.80  
  Purchase #3 $241.54   7.167%   $258.8512   $258.85   $258.85   $258.90  
  Purchase #4 $206.47   13.868%   $235.1033   $235.10   $235.10   $235.10  
  Purchase #5 $43.85   8.243%   $47.4646   $47.46   $47.45   $47.50  
  Purchase #6 $72.61   8.253%   $78.6025   $78.60   $78.60   $78.60  
  Purchase #7 $176.66   6.157%   $187.537   $187.54   $187.55   $187.50  
  7 purchase totals = $1,166.50       $1,262.0419   $1,262.04   $1,262.05   $1,262.00