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 $206.94   4.253%   $215.7412   $215.74   $215.75   $215.70  
  Purchase #2 $197.77   13.689%   $224.8427   $224.84   $224.85   $224.80  
  Purchase #3 $142.52   13.396%   $161.612   $161.61   $161.60   $161.60  
  Purchase #4 $201.61   3.108%   $207.876   $207.88   $207.90   $207.90  
  Purchase #5 $162.76   3.612%   $168.6389   $168.64   $168.65   $168.60  
  Purchase #6 $250.99   8.258%   $271.7168   $271.72   $271.70   $271.70  
  Purchase #7 $190.65   10.407%   $210.4909   $210.49   $210.50   $210.50  
  7 purchase totals = $1,353.24       $1,460.9185   $1,460.92   $1,460.95   $1,460.80