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 $119.41   5.690%   $126.2044   $126.20   $126.20   $126.20  
  Purchase #2 $242.73   3.835%   $252.0387   $252.04   $252.05   $252.00  
  Purchase #3 $226.32   7.267%   $242.7667   $242.77   $242.75   $242.80  
  Purchase #4 $191.90   9.323%   $209.7908   $209.79   $209.80   $209.80  
  Purchase #5 $190.65   6.554%   $203.1452   $203.15   $203.15   $203.10  
  Purchase #6 $207.37   8.726%   $225.4651   $225.47   $225.45   $225.50  
  Purchase #7 $41.60   3.703%   $43.1404   $43.14   $43.15   $43.10  
  7 purchase totals = $1,219.98       $1,302.5513   $1,302.56   $1,302.55   $1,302.50