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 $67.98   12.275%   $76.3245   $76.32   $76.30   $76.30  
  Purchase #2 $152.78   3.378%   $157.9409   $157.94   $157.95   $157.90  
  Purchase #3 $171.38   5.517%   $180.835   $180.84   $180.85   $180.80  
  Purchase #4 $123.28   8.234%   $133.4309   $133.43   $133.45   $133.40  
  Purchase #5 $201.69   6.444%   $214.6869   $214.69   $214.70   $214.70  
  Purchase #6 $145.68   11.857%   $162.9533   $162.95   $162.95   $163.00  
  Purchase #7 $182.82   9.792%   $200.7217   $200.72   $200.70   $200.70  
  7 purchase totals = $1,045.61       $1,126.8932   $1,126.89   $1,126.90   $1,126.80