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 $208.47   9.503%   $228.2809   $228.28   $228.30   $228.30  
  Purchase #2 $237.92   5.755%   $251.6123   $251.61   $251.60   $251.60  
  Purchase #3 $165.43   8.557%   $179.5858   $179.59   $179.60   $179.60  
  Purchase #4 $50.37   10.595%   $55.7067   $55.71   $55.70   $55.70  
  Purchase #5 $212.85   7.364%   $228.5243   $228.52   $228.50   $228.50  
  Purchase #6 $149.30   11.353%   $166.25   $166.25   $166.25   $166.30  
  Purchase #7 $237.70   12.157%   $266.5972   $266.60   $266.60   $266.60  
  7 purchase totals = $1,262.04       $1,376.5572   $1,376.56   $1,376.55   $1,376.60