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 $233.51   8.626%   $253.6526   $253.65   $253.65   $253.70  
  Purchase #2 $238.42   10.113%   $262.5314   $262.53   $262.55   $262.50  
  Purchase #3 $103.63   8.593%   $112.5349   $112.53   $112.55   $112.50  
  Purchase #4 $186.74   4.825%   $195.7502   $195.75   $195.75   $195.80  
  Purchase #5 $243.46   7.335%   $261.3178   $261.32   $261.30   $261.30  
  Purchase #6 $193.63   8.548%   $210.1815   $210.18   $210.20   $210.20  
  Purchase #7 $80.61   12.289%   $90.5162   $90.52   $90.50   $90.50  
  7 purchase totals = $1,280.00       $1,386.4846   $1,386.48   $1,386.50   $1,386.50