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 $85.97   10.773%   $95.2315   $95.23   $95.25   $95.20  
  Purchase #2 $50.32   11.585%   $56.1496   $56.15   $56.15   $56.10  
  Purchase #3 $125.75   3.144%   $129.7036   $129.70   $129.70   $129.70  
  Purchase #4 $153.91   8.205%   $166.5383   $166.54   $166.55   $166.50  
  Purchase #5 $14.79   9.596%   $16.2092   $16.21   $16.20   $16.20  
  Purchase #6 $45.51   3.806%   $47.2421   $47.24   $47.25   $47.20  
  Purchase #7 $208.69   12.774%   $235.3481   $235.35   $235.35   $235.30  
  7 purchase totals = $684.94       $746.4224   $746.42   $746.45   $746.20