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 $214.96   13.489%   $243.956   $243.96   $243.95   $244.00  
  Purchase #2 $104.94   10.245%   $115.6911   $115.69   $115.70   $115.70  
  Purchase #3 $145.49   6.712%   $155.2553   $155.26   $155.25   $155.30  
  Purchase #4 $239.73   4.281%   $249.9928   $249.99   $250.00   $250.00  
  Purchase #5 $77.69   3.425%   $80.3509   $80.35   $80.35   $80.40  
  Purchase #6 $18.89   5.839%   $19.993   $19.99   $20.00   $20.00  
  Purchase #7 $180.97   12.187%   $203.0248   $203.02   $203.00   $203.00  
  7 purchase totals = $982.67       $1,068.2639   $1,068.26   $1,068.25   $1,068.40