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 $67.52   8.507%   $73.2639   $73.26   $73.25   $73.30  
  Purchase #2 $116.26   8.439%   $126.0712   $126.07   $126.05   $126.10  
  Purchase #3 $240.85   10.849%   $266.9798   $266.98   $267.00   $267.00  
  Purchase #4 $50.79   13.865%   $57.832   $57.83   $57.85   $57.80  
  Purchase #5 $153.45   8.634%   $166.6989   $166.70   $166.70   $166.70  
  Purchase #6 $215.48   13.114%   $243.738   $243.74   $243.75   $243.70  
  Purchase #7 $43.49   10.317%   $47.9769   $47.98   $48.00   $48.00  
  7 purchase totals = $887.84       $982.5607   $982.56   $982.60   $982.60