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 $164.79   6.593%   $175.6546   $175.65   $175.65   $175.70  
  Purchase #2 $118.43   4.672%   $123.963   $123.96   $123.95   $124.00  
  Purchase #3 $142.96   8.614%   $155.2746   $155.27   $155.25   $155.30  
  Purchase #4 $224.91   6.552%   $239.6461   $239.65   $239.65   $239.60  
  Purchase #5 $99.68   6.816%   $106.4742   $106.47   $106.45   $106.50  
  Purchase #6 $92.64   12.190%   $103.9328   $103.93   $103.95   $103.90  
  Purchase #7 $52.63   8.269%   $56.982   $56.98   $57.00   $57.00  
  7 purchase totals = $896.04       $961.9273   $961.91   $961.90   $962.00