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 $149.38   8.644%   $162.2924   $162.29   $162.30   $162.30  
  Purchase #2 $190.95   8.391%   $206.9726   $206.97   $206.95   $207.00  
  Purchase #3 $200.78   7.813%   $216.4669   $216.47   $216.45   $216.50  
  Purchase #4 $163.52   3.345%   $168.9897   $168.99   $169.00   $169.00  
  Purchase #5 $135.57   11.551%   $151.2297   $151.23   $151.25   $151.20  
  Purchase #6 $164.54   13.500%   $186.7529   $186.75   $186.75   $186.80  
  Purchase #7 $247.91   12.522%   $278.9533   $278.95   $278.95   $279.00  
  7 purchase totals = $1,252.65       $1,371.6575   $1,371.65   $1,371.65   $1,371.80