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 $245.33   5.852%   $259.6867   $259.69   $259.70   $259.70  
  Purchase #2 $186.82   13.423%   $211.8968   $211.90   $211.90   $211.90  
  Purchase #3 $169.95   9.252%   $185.6738   $185.67   $185.65   $185.70  
  Purchase #4 $50.73   3.444%   $52.4771   $52.48   $52.50   $52.50  
  Purchase #5 $141.60   6.794%   $151.2203   $151.22   $151.20   $151.20  
  Purchase #6 $246.44   8.140%   $266.5002   $266.50   $266.50   $266.50  
  Purchase #7 $119.44   5.103%   $125.535   $125.54   $125.55   $125.50  
  7 purchase totals = $1,160.31       $1,252.9899   $1,253.00   $1,253.00   $1,253.00