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 $177.63   11.238%   $197.5921   $197.59   $197.60   $197.60  
  Purchase #2 $176.50   10.635%   $195.2708   $195.27   $195.25   $195.30  
  Purchase #3 $33.67   6.463%   $35.8461   $35.85   $35.85   $35.80  
  Purchase #4 $98.31   10.653%   $108.783   $108.78   $108.80   $108.80  
  Purchase #5 $240.86   13.846%   $274.2095   $274.21   $274.20   $274.20  
  Purchase #6 $247.26   8.574%   $268.4601   $268.46   $268.45   $268.50  
  Purchase #7 $240.41   10.486%   $265.6194   $265.62   $265.60   $265.60  
  7 purchase totals = $1,214.64       $1,345.7810   $1,345.78   $1,345.75   $1,345.80