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 $68.35   8.304%   $74.0258   $74.03   $74.05   $74.00  
  Purchase #2 $59.93   11.292%   $66.6973   $66.70   $66.70   $66.70  
  Purchase #3 $26.71   6.308%   $28.3949   $28.39   $28.40   $28.40  
  Purchase #4 $47.85   9.173%   $52.2393   $52.24   $52.25   $52.20  
  Purchase #5 $197.49   12.859%   $222.8852   $222.89   $222.90   $222.90  
  Purchase #6 $148.32   6.571%   $158.0661   $158.07   $158.05   $158.10  
  Purchase #7 $151.91   11.705%   $169.6911   $169.69   $169.70   $169.70  
  7 purchase totals = $700.56       $771.9997   $772.01   $772.05   $772.00