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 $62.31   8.571%   $67.6506   $67.65   $67.65   $67.70  
  Purchase #2 $222.44   7.150%   $238.3445   $238.34   $238.35   $238.30  
  Purchase #3 $190.43   4.488%   $198.9765   $198.98   $199.00   $199.00  
  Purchase #4 $89.75   5.161%   $94.382   $94.38   $94.40   $94.40  
  Purchase #5 $58.89   3.318%   $60.844   $60.84   $60.85   $60.80  
  Purchase #6 $163.60   5.223%   $172.1448   $172.14   $172.15   $172.10  
  Purchase #7 $220.27   11.574%   $245.764   $245.76   $245.75   $245.80  
  7 purchase totals = $1,007.69       $1,078.1064   $1,078.09   $1,078.15   $1,078.10