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 $205.52   9.361%   $224.7587   $224.76   $224.75   $224.80  
  Purchase #2 $143.25   9.733%   $157.1925   $157.19   $157.20   $157.20  
  Purchase #3 $240.29   3.208%   $247.9985   $248.00   $248.00   $248.00  
  Purchase #4 $81.69   5.662%   $86.3153   $86.32   $86.30   $86.30  
  Purchase #5 $27.39   6.500%   $29.1704   $29.17   $29.15   $29.20  
  Purchase #6 $239.75   5.341%   $252.555   $252.56   $252.55   $252.60  
  Purchase #7 $49.28   10.517%   $54.4628   $54.46   $54.45   $54.50  
  7 purchase totals = $987.17       $1,052.4532   $1,052.46   $1,052.40   $1,052.60