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 $108.46   5.728%   $114.6726   $114.67   $114.65   $114.70  
  Purchase #2 $52.30   8.802%   $56.9034   $56.90   $56.90   $56.90  
  Purchase #3 $172.91   12.554%   $194.6171   $194.62   $194.60   $194.60  
  Purchase #4 $238.40   12.116%   $267.2845   $267.28   $267.30   $267.30  
  Purchase #5 $134.93   3.491%   $139.6404   $139.64   $139.65   $139.60  
  Purchase #6 $49.53   12.275%   $55.6098   $55.61   $55.60   $55.60  
  Purchase #7 $181.98   12.259%   $204.2889   $204.29   $204.30   $204.30  
  7 purchase totals = $938.51       $1,033.0167   $1,033.01   $1,033.00   $1,033.00