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 $88.75   11.112%   $98.6119   $98.61   $98.60   $98.60  
  Purchase #2 $221.48   11.142%   $246.1573   $246.16   $246.15   $246.20  
  Purchase #3 $208.40   11.470%   $232.3035   $232.30   $232.30   $232.30  
  Purchase #4 $207.44   13.203%   $234.8283   $234.83   $234.85   $234.80  
  Purchase #5 $232.43   12.120%   $260.6005   $260.60   $260.60   $260.60  
  Purchase #6 $52.35   7.176%   $56.1066   $56.11   $56.10   $56.10  
  Purchase #7 $35.99   7.516%   $38.695   $38.70   $38.70   $38.70  
  7 purchase totals = $1,046.84       $1,167.3031   $1,167.31   $1,167.30   $1,167.30