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 $157.58   7.684%   $169.6884   $169.69   $169.70   $169.70  
  Purchase #2 $163.98   4.105%   $170.7114   $170.71   $170.70   $170.70  
  Purchase #3 $37.26   4.395%   $38.8976   $38.90   $38.90   $38.90  
  Purchase #4 $59.44   4.413%   $62.0631   $62.06   $62.05   $62.10  
  Purchase #5 $167.28   10.156%   $184.269   $184.27   $184.25   $184.30  
  Purchase #6 $202.28   5.241%   $212.8815   $212.88   $212.90   $212.90  
  Purchase #7 $245.44   8.145%   $265.4311   $265.43   $265.45   $265.40  
  7 purchase totals = $1,033.26       $1,103.9421   $1,103.94   $1,103.95   $1,104.00