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 $175.47   11.658%   $195.9263   $195.93   $195.95   $195.90  
  Purchase #2 $133.94   12.521%   $150.7106   $150.71   $150.70   $150.70  
  Purchase #3 $69.74   10.216%   $76.8646   $76.86   $76.85   $76.90  
  Purchase #4 $38.34   4.613%   $40.1086   $40.11   $40.10   $40.10  
  Purchase #5 $48.58   13.395%   $55.0873   $55.09   $55.10   $55.10  
  Purchase #6 $236.73   11.122%   $263.0591   $263.06   $263.05   $263.10  
  Purchase #7 $155.81   5.398%   $164.2206   $164.22   $164.20   $164.20  
  7 purchase totals = $858.61       $945.9771   $945.98   $945.95   $946.00