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 $32.28   4.567%   $33.7542   $33.75   $33.75   $33.80  
  Purchase #2 $216.26   13.779%   $246.0585   $246.06   $246.05   $246.10  
  Purchase #3 $207.70   6.678%   $221.5702   $221.57   $221.55   $221.60  
  Purchase #4 $69.78   4.681%   $73.0464   $73.05   $73.05   $73.00  
  Purchase #5 $133.40   10.440%   $147.327   $147.33   $147.35   $147.30  
  Purchase #6 $244.99   6.599%   $261.1569   $261.16   $261.15   $261.20  
  Purchase #7 $20.96   13.455%   $23.7802   $23.78   $23.80   $23.80  
  7 purchase totals = $925.37       $1,006.6934   $1,006.70   $1,006.70   $1,006.80