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 $103.41   10.237%   $113.9961   $114.00   $114.00   $114.00  
  Purchase #2 $146.52   6.515%   $156.0658   $156.07   $156.05   $156.10  
  Purchase #3 $74.91   10.840%   $83.0302   $83.03   $83.05   $83.00  
  Purchase #4 $209.55   3.204%   $216.264   $216.26   $216.25   $216.30  
  Purchase #5 $218.76   10.238%   $241.1566   $241.16   $241.15   $241.20  
  Purchase #6 $180.96   6.665%   $193.021   $193.02   $193.00   $193.00  
  Purchase #7 $34.49   10.183%   $38.0021   $38.00   $38.00   $38.00  
  7 purchase totals = $968.60       $1,041.5358   $1,041.54   $1,041.50   $1,041.60