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 $162.81   4.229%   $169.6952   $169.70   $169.70   $169.70  
  Purchase #2 $168.53   4.692%   $176.4374   $176.44   $176.45   $176.40  
  Purchase #3 $97.98   12.409%   $110.1383   $110.14   $110.15   $110.10  
  Purchase #4 $50.26   12.388%   $56.4862   $56.49   $56.50   $56.50  
  Purchase #5 $52.50   9.267%   $57.3652   $57.37   $57.35   $57.40  
  Purchase #6 $187.66   4.486%   $196.0784   $196.08   $196.10   $196.10  
  Purchase #7 $227.89   7.335%   $244.6057   $244.61   $244.60   $244.60  
  7 purchase totals = $947.63       $1,010.8064   $1,010.83   $1,010.85   $1,010.80