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 $43.25   7.842%   $46.6417   $46.64   $46.65   $46.60  
  Purchase #2 $149.97   11.373%   $167.0261   $167.03   $167.05   $167.00  
  Purchase #3 $178.54   12.688%   $201.1932   $201.19   $201.20   $201.20  
  Purchase #4 $109.79   11.487%   $122.4016   $122.40   $122.40   $122.40  
  Purchase #5 $239.81   7.520%   $257.8437   $257.84   $257.85   $257.80  
  Purchase #6 $114.65   10.377%   $126.5472   $126.55   $126.55   $126.50  
  Purchase #7 $207.84   11.287%   $231.2989   $231.30   $231.30   $231.30  
  7 purchase totals = $1,043.85       $1,152.9524   $1,152.95   $1,153.00   $1,152.80