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 $95.28   11.760%   $106.4849   $106.48   $106.50   $106.50  
  Purchase #2 $158.48   11.446%   $176.6196   $176.62   $176.60   $176.60  
  Purchase #3 $231.75   9.417%   $253.5739   $253.57   $253.55   $253.60  
  Purchase #4 $94.63   9.317%   $103.4467   $103.45   $103.45   $103.40  
  Purchase #5 $245.55   4.808%   $257.356   $257.36   $257.35   $257.40  
  Purchase #6 $123.43   8.103%   $133.4315   $133.43   $133.45   $133.40  
  Purchase #7 $115.44   13.531%   $131.0602   $131.06   $131.05   $131.10  
  7 purchase totals = $1,064.56       $1,161.9728   $1,161.97   $1,161.95   $1,162.00