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 $214.94   5.396%   $226.5382   $226.54   $226.55   $226.50  
  Purchase #2 $63.84   6.298%   $67.8606   $67.86   $67.85   $67.90  
  Purchase #3 $94.82   13.431%   $107.5553   $107.56   $107.55   $107.60  
  Purchase #4 $174.48   5.450%   $183.9892   $183.99   $184.00   $184.00  
  Purchase #5 $133.60   6.721%   $142.5793   $142.58   $142.60   $142.60  
  Purchase #6 $126.95   12.189%   $142.4239   $142.42   $142.40   $142.40  
  Purchase #7 $149.66   9.712%   $164.195   $164.20   $164.20   $164.20  
  7 purchase totals = $958.29       $1,035.1415   $1,035.15   $1,035.15   $1,035.20