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 $153.87   5.277%   $161.9897   $161.99   $162.00   $162.00  
  Purchase #2 $244.95   8.508%   $265.7903   $265.79   $265.80   $265.80  
  Purchase #3 $154.76   4.806%   $162.1978   $162.20   $162.20   $162.20  
  Purchase #4 $166.83   12.330%   $187.4001   $187.40   $187.40   $187.40  
  Purchase #5 $53.46   5.548%   $56.426   $56.43   $56.45   $56.40  
  Purchase #6 $124.52   13.709%   $141.5904   $141.59   $141.60   $141.60  
  Purchase #7 $217.44   4.276%   $226.7377   $226.74   $226.75   $226.70  
  7 purchase totals = $1,115.83       $1,202.1320   $1,202.14   $1,202.20   $1,202.10