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 $202.26   8.289%   $219.0253   $219.03   $219.05   $219.00  
  Purchase #2 $29.25   12.107%   $32.7913   $32.79   $32.80   $32.80  
  Purchase #3 $153.28   8.628%   $166.505   $166.51   $166.50   $166.50  
  Purchase #4 $227.77   3.781%   $236.382   $236.38   $236.40   $236.40  
  Purchase #5 $136.95   12.688%   $154.3262   $154.33   $154.35   $154.30  
  Purchase #6 $208.71   6.284%   $221.8253   $221.83   $221.85   $221.80  
  Purchase #7 $136.92   10.610%   $151.4472   $151.45   $151.45   $151.40  
  7 purchase totals = $1,095.14       $1,182.3023   $1,182.32   $1,182.40   $1,182.20