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 $112.88   5.860%   $119.4948   $119.49   $119.50   $119.50  
  Purchase #2 $105.61   12.368%   $118.6718   $118.67   $118.65   $118.70  
  Purchase #3 $144.73   5.247%   $152.324   $152.32   $152.30   $152.30  
  Purchase #4 $231.64   5.318%   $243.9586   $243.96   $243.95   $244.00  
  Purchase #5 $115.46   12.603%   $130.0114   $130.01   $130.00   $130.00  
  Purchase #6 $218.30   4.337%   $227.7677   $227.77   $227.75   $227.80  
  Purchase #7 $104.46   10.425%   $115.35   $115.35   $115.35   $115.40  
  7 purchase totals = $1,033.08       $1,107.5783   $1,107.57   $1,107.50   $1,107.70