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 $213.75   3.299%   $220.8016   $220.80   $220.80   $220.80  
  Purchase #2 $39.97   11.821%   $44.6949   $44.69   $44.70   $44.70  
  Purchase #3 $237.82   4.495%   $248.51   $248.51   $248.50   $248.50  
  Purchase #4 $183.83   5.445%   $193.8395   $193.84   $193.85   $193.80  
  Purchase #5 $72.63   6.845%   $77.6015   $77.60   $77.60   $77.60  
  Purchase #6 $130.36   3.450%   $134.8574   $134.86   $134.85   $134.90  
  Purchase #7 $82.46   13.730%   $93.7818   $93.78   $93.80   $93.80  
  7 purchase totals = $960.82       $1,014.0867   $1,014.08   $1,014.10   $1,014.10