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 $176.26   4.820%   $184.7557   $184.76   $184.75   $184.80  
  Purchase #2 $212.90   12.475%   $239.4593   $239.46   $239.45   $239.50  
  Purchase #3 $248.44   11.815%   $277.7932   $277.79   $277.80   $277.80  
  Purchase #4 $218.45   6.245%   $232.0922   $232.09   $232.10   $232.10  
  Purchase #5 $224.78   10.403%   $248.1639   $248.16   $248.15   $248.20  
  Purchase #6 $202.28   6.761%   $215.9562   $215.96   $215.95   $216.00  
  Purchase #7 $75.80   11.459%   $84.4859   $84.49   $84.50   $84.50  
  7 purchase totals = $1,358.91       $1,482.7064   $1,482.71   $1,482.70   $1,482.90