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 $59.83   5.691%   $63.2349   $63.23   $63.25   $63.20  
  Purchase #2 $65.63   6.241%   $69.726   $69.73   $69.75   $69.70  
  Purchase #3 $74.77   7.734%   $80.5527   $80.55   $80.55   $80.60  
  Purchase #4 $204.38   7.546%   $219.8025   $219.80   $219.80   $219.80  
  Purchase #5 $214.71   11.485%   $239.3694   $239.37   $239.35   $239.40  
  Purchase #6 $194.95   12.717%   $219.7418   $219.74   $219.75   $219.70  
  Purchase #7 $211.68   7.238%   $227.0014   $227.00   $227.00   $227.00  
  7 purchase totals = $1,025.95       $1,119.4287   $1,119.42   $1,119.45   $1,119.40