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 $182.60   13.134%   $206.5827   $206.58   $206.60   $206.60  
  Purchase #2 $120.46   5.278%   $126.8179   $126.82   $126.80   $126.80  
  Purchase #3 $93.88   3.854%   $97.4981   $97.50   $97.50   $97.50  
  Purchase #4 $196.50   4.187%   $204.7275   $204.73   $204.75   $204.70  
  Purchase #5 $229.52   8.403%   $248.8066   $248.81   $248.80   $248.80  
  Purchase #6 $84.80   11.774%   $94.7844   $94.78   $94.80   $94.80  
  Purchase #7 $31.34   11.119%   $34.8247   $34.82   $34.80   $34.80  
  7 purchase totals = $939.10       $1,014.0419   $1,014.04   $1,014.05   $1,014.00