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 $64.69   10.371%   $71.399   $71.40   $71.40   $71.40  
  Purchase #2 $104.89   8.403%   $113.7039   $113.70   $113.70   $113.70  
  Purchase #3 $168.85   5.290%   $177.7822   $177.78   $177.80   $177.80  
  Purchase #4 $221.75   11.135%   $246.4419   $246.44   $246.45   $246.40  
  Purchase #5 $153.67   7.366%   $164.9893   $164.99   $165.00   $165.00  
  Purchase #6 $80.87   10.414%   $89.2918   $89.29   $89.30   $89.30  
  Purchase #7 $193.32   9.872%   $212.4046   $212.40   $212.40   $212.40  
  7 purchase totals = $988.04       $1,076.0127   $1,076.00   $1,076.05   $1,076.00