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 $114.59   13.619%   $130.196   $130.20   $130.20   $130.20  
  Purchase #2 $12.87   4.166%   $13.4062   $13.41   $13.40   $13.40  
  Purchase #3 $164.63   12.432%   $185.0968   $185.10   $185.10   $185.10  
  Purchase #4 $187.67   7.628%   $201.9855   $201.99   $202.00   $202.00  
  Purchase #5 $119.28   5.285%   $125.5839   $125.58   $125.60   $125.60  
  Purchase #6 $151.34   13.128%   $171.2079   $171.21   $171.20   $171.20  
  Purchase #7 $177.52   11.280%   $197.5443   $197.54   $197.55   $197.50  
  7 purchase totals = $927.90       $1,025.0206   $1,025.03   $1,025.05   $1,025.00