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 $214.48   8.625%   $232.9789   $232.98   $233.00   $233.00  
  Purchase #2 $123.55   7.385%   $132.6742   $132.67   $132.65   $132.70  
  Purchase #3 $87.27   3.194%   $90.0574   $90.06   $90.05   $90.10  
  Purchase #4 $76.63   5.627%   $80.942   $80.94   $80.95   $80.90  
  Purchase #5 $108.74   3.645%   $112.7036   $112.70   $112.70   $112.70  
  Purchase #6 $36.55   5.141%   $38.429   $38.43   $38.45   $38.40  
  Purchase #7 $61.81   11.180%   $68.7204   $68.72   $68.70   $68.70  
  7 purchase totals = $709.03       $756.5055   $756.50   $756.50   $756.50