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 $162.51   9.269%   $177.5731   $177.57   $177.55   $177.60  
  Purchase #2 $244.46   13.337%   $277.0636   $277.06   $277.05   $277.10  
  Purchase #3 $83.55   8.394%   $90.5632   $90.56   $90.55   $90.60  
  Purchase #4 $243.81   11.408%   $271.6238   $271.62   $271.60   $271.60  
  Purchase #5 $34.33   8.802%   $37.3517   $37.35   $37.35   $37.40  
  Purchase #6 $74.42   3.440%   $76.98   $76.98   $77.00   $77.00  
  Purchase #7 $226.84   12.602%   $255.4264   $255.43   $255.45   $255.40  
  7 purchase totals = $1,069.92       $1,186.5818   $1,186.57   $1,186.55   $1,186.70