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 $68.80   4.423%   $71.843   $71.84   $71.85   $71.80  
  Purchase #2 $236.29   4.446%   $246.7955   $246.80   $246.80   $246.80  
  Purchase #3 $88.88   10.354%   $98.0826   $98.08   $98.10   $98.10  
  Purchase #4 $212.45   3.747%   $220.4105   $220.41   $220.40   $220.40  
  Purchase #5 $146.61   11.671%   $163.7209   $163.72   $163.70   $163.70  
  Purchase #6 $129.76   4.615%   $135.7484   $135.75   $135.75   $135.70  
  Purchase #7 $111.94   3.599%   $115.9687   $115.97   $115.95   $116.00  
  7 purchase totals = $994.73       $1,052.5696   $1,052.57   $1,052.55   $1,052.50