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 $119.77   5.323%   $126.1454   $126.15   $126.15   $126.10  
  Purchase #2 $189.62   9.380%   $207.4064   $207.41   $207.40   $207.40  
  Purchase #3 $77.69   12.658%   $87.524   $87.52   $87.50   $87.50  
  Purchase #4 $166.49   11.537%   $185.698   $185.70   $185.70   $185.70  
  Purchase #5 $162.34   10.309%   $179.0756   $179.08   $179.10   $179.10  
  Purchase #6 $23.41   5.293%   $24.6491   $24.65   $24.65   $24.60  
  Purchase #7 $96.76   10.551%   $106.9691   $106.97   $106.95   $107.00  
  7 purchase totals = $836.08       $917.4676   $917.48   $917.45   $917.40