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 $44.39   4.822%   $46.5305   $46.53   $46.55   $46.50  
  Purchase #2 $184.59   3.860%   $191.7152   $191.72   $191.70   $191.70  
  Purchase #3 $59.73   7.837%   $64.411   $64.41   $64.40   $64.40  
  Purchase #4 $237.75   11.489%   $265.0651   $265.07   $265.05   $265.10  
  Purchase #5 $113.74   13.780%   $129.4134   $129.41   $129.40   $129.40  
  Purchase #6 $209.91   6.403%   $223.3505   $223.35   $223.35   $223.40  
  Purchase #7 $183.64   13.844%   $209.0631   $209.06   $209.05   $209.10  
  7 purchase totals = $1,033.75       $1,129.5488   $1,129.55   $1,129.50   $1,129.60