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 $83.72   13.581%   $95.09   $95.09   $95.10   $95.10  
  Purchase #2 $84.91   12.441%   $95.4737   $95.47   $95.45   $95.50  
  Purchase #3 $112.57   8.298%   $121.9111   $121.91   $121.90   $121.90  
  Purchase #4 $216.65   5.813%   $229.2439   $229.24   $229.25   $229.20  
  Purchase #5 $136.26   3.801%   $141.4392   $141.44   $141.45   $141.40  
  Purchase #6 $131.63   12.159%   $147.6349   $147.63   $147.65   $147.60  
  Purchase #7 $218.74   9.419%   $239.3431   $239.34   $239.35   $239.30  
  7 purchase totals = $984.48       $1,070.1359   $1,070.12   $1,070.15   $1,070.00