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 $208.33   7.604%   $224.1714   $224.17   $224.15   $224.20  
  Purchase #2 $100.79   6.688%   $107.5308   $107.53   $107.55   $107.50  
  Purchase #3 $117.76   5.299%   $124.0001   $124.00   $124.00   $124.00  
  Purchase #4 $107.46   11.733%   $120.0683   $120.07   $120.05   $120.10  
  Purchase #5 $170.30   9.803%   $186.9945   $186.99   $187.00   $187.00  
  Purchase #6 $158.65   11.774%   $177.3295   $177.33   $177.35   $177.30  
  Purchase #7 $184.42   11.870%   $206.3107   $206.31   $206.30   $206.30  
  7 purchase totals = $1,047.71       $1,146.4053   $1,146.40   $1,146.40   $1,146.40