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 $86.70   8.410%   $93.9915   $93.99   $94.00   $94.00  
  Purchase #2 $244.64   10.823%   $271.1174   $271.12   $271.10   $271.10  
  Purchase #3 $245.76   11.180%   $273.236   $273.24   $273.25   $273.20  
  Purchase #4 $217.55   13.359%   $246.6125   $246.61   $246.60   $246.60  
  Purchase #5 $27.26   7.468%   $29.2958   $29.30   $29.30   $29.30  
  Purchase #6 $124.71   10.731%   $138.0926   $138.09   $138.10   $138.10  
  Purchase #7 $131.42   8.403%   $142.4632   $142.46   $142.45   $142.50  
  7 purchase totals = $1,078.04       $1,194.8090   $1,194.81   $1,194.80   $1,194.80