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 $46.31   3.660%   $48.0049   $48.00   $48.00   $48.00  
  Purchase #2 $119.92   8.662%   $130.3075   $130.31   $130.30   $130.30  
  Purchase #3 $65.57   11.771%   $73.2882   $73.29   $73.30   $73.30  
  Purchase #4 $231.33   7.733%   $249.2187   $249.22   $249.20   $249.20  
  Purchase #5 $201.43   9.271%   $220.1046   $220.10   $220.10   $220.10  
  Purchase #6 $215.74   7.379%   $231.6595   $231.66   $231.65   $231.70  
  Purchase #7 $82.66   4.465%   $86.3508   $86.35   $86.35   $86.40  
  7 purchase totals = $962.96       $1,038.9342   $1,038.93   $1,038.90   $1,039.00