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 $195.97   7.808%   $211.2713   $211.27   $211.25   $211.30  
  Purchase #2 $71.41   9.472%   $78.174   $78.17   $78.15   $78.20  
  Purchase #3 $162.32   9.103%   $177.096   $177.10   $177.10   $177.10  
  Purchase #4 $151.97   8.538%   $164.9452   $164.95   $164.95   $164.90  
  Purchase #5 $209.54   13.375%   $237.566   $237.57   $237.55   $237.60  
  Purchase #6 $101.37   8.388%   $109.8729   $109.87   $109.85   $109.90  
  Purchase #7 $199.57   12.364%   $224.2448   $224.24   $224.25   $224.20  
  7 purchase totals = $1,092.15       $1,203.1702   $1,203.17   $1,203.10   $1,203.20