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 $215.62   8.136%   $233.1628   $233.16   $233.15   $233.20  
  Purchase #2 $240.58   5.693%   $254.2762   $254.28   $254.30   $254.30  
  Purchase #3 $66.29   10.326%   $73.1351   $73.14   $73.15   $73.10  
  Purchase #4 $57.78   3.762%   $59.9537   $59.95   $59.95   $60.00  
  Purchase #5 $154.35   11.414%   $171.9675   $171.97   $171.95   $172.00  
  Purchase #6 $24.97   8.124%   $26.9986   $27.00   $27.00   $27.00  
  Purchase #7 $202.68   6.166%   $215.1772   $215.18   $215.20   $215.20  
  7 purchase totals = $962.27       $1,034.6711   $1,034.68   $1,034.70   $1,034.80