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 $59.89   6.653%   $63.8745   $63.87   $63.85   $63.90  
  Purchase #2 $241.50   11.655%   $269.6468   $269.65   $269.65   $269.60  
  Purchase #3 $64.64   11.368%   $71.9883   $71.99   $72.00   $72.00  
  Purchase #4 $245.45   5.409%   $258.7264   $258.73   $258.75   $258.70  
  Purchase #5 $171.80   3.607%   $177.9968   $178.00   $178.00   $178.00  
  Purchase #6 $174.31   4.467%   $182.0964   $182.10   $182.10   $182.10  
  Purchase #7 $131.62   7.207%   $141.1059   $141.11   $141.10   $141.10  
  7 purchase totals = $1,089.21       $1,165.4351   $1,165.45   $1,165.45   $1,165.40