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 $201.33   6.364%   $214.1426   $214.14   $214.15   $214.10  
  Purchase #2 $196.61   5.107%   $206.6509   $206.65   $206.65   $206.70  
  Purchase #3 $23.68   9.377%   $25.9005   $25.90   $25.90   $25.90  
  Purchase #4 $159.86   12.176%   $179.3246   $179.32   $179.30   $179.30  
  Purchase #5 $118.32   10.366%   $130.5851   $130.59   $130.60   $130.60  
  Purchase #6 $146.63   11.657%   $163.7227   $163.72   $163.70   $163.70  
  Purchase #7 $86.66   6.501%   $92.2938   $92.29   $92.30   $92.30  
  7 purchase totals = $933.09       $1,012.6202   $1,012.61   $1,012.60   $1,012.60