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 $53.70   12.365%   $60.34   $60.34   $60.35   $60.30  
  Purchase #2 $126.70   12.493%   $142.5286   $142.53   $142.55   $142.50  
  Purchase #3 $133.90   10.650%   $148.1604   $148.16   $148.15   $148.20  
  Purchase #4 $208.81   4.158%   $217.4923   $217.49   $217.50   $217.50  
  Purchase #5 $194.26   9.460%   $212.637   $212.64   $212.65   $212.60  
  Purchase #6 $165.33   4.457%   $172.6988   $172.70   $172.70   $172.70  
  Purchase #7 $236.29   6.518%   $251.6914   $251.69   $251.70   $251.70  
  7 purchase totals = $1,118.99       $1,205.5485   $1,205.55   $1,205.60   $1,205.50