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 $22.54   13.799%   $25.6503   $25.65   $25.65   $25.70  
  Purchase #2 $86.41   13.513%   $98.0866   $98.09   $98.10   $98.10  
  Purchase #3 $87.27   4.677%   $91.3516   $91.35   $91.35   $91.40  
  Purchase #4 $67.52   11.537%   $75.3098   $75.31   $75.30   $75.30  
  Purchase #5 $97.33   8.552%   $105.6537   $105.65   $105.65   $105.70  
  Purchase #6 $196.60   4.831%   $206.0977   $206.10   $206.10   $206.10  
  Purchase #7 $134.67   11.749%   $150.4924   $150.49   $150.50   $150.50  
  7 purchase totals = $692.34       $752.6421   $752.64   $752.65   $752.80