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 $41.84   5.484%   $44.1345   $44.13   $44.15   $44.10  
  Purchase #2 $123.95   9.613%   $135.8653   $135.87   $135.85   $135.90  
  Purchase #3 $50.55   3.448%   $52.293   $52.29   $52.30   $52.30  
  Purchase #4 $73.79   10.736%   $81.7121   $81.71   $81.70   $81.70  
  Purchase #5 $14.60   11.414%   $16.2664   $16.27   $16.25   $16.30  
  Purchase #6 $59.28   3.793%   $61.5285   $61.53   $61.55   $61.50  
  Purchase #7 $65.72   13.857%   $74.8268   $74.83   $74.85   $74.80  
  7 purchase totals = $429.73       $466.6266   $466.63   $466.65   $466.60