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 $61.27   11.335%   $68.215   $68.22   $68.20   $68.20  
  Purchase #2 $244.64   3.586%   $253.4128   $253.41   $253.40   $253.40  
  Purchase #3 $17.85   7.795%   $19.2414   $19.24   $19.25   $19.20  
  Purchase #4 $61.31   6.268%   $65.1529   $65.15   $65.15   $65.20  
  Purchase #5 $175.28   13.449%   $198.8534   $198.85   $198.85   $198.90  
  Purchase #6 $36.59   3.534%   $37.8831   $37.88   $37.90   $37.90  
  Purchase #7 $97.98   6.359%   $104.2105   $104.21   $104.20   $104.20  
  7 purchase totals = $694.92       $746.9691   $746.96   $746.95   $747.00