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 $219.26   13.328%   $248.483   $248.48   $248.50   $248.50  
  Purchase #2 $159.87   7.196%   $171.3742   $171.37   $171.35   $171.40  
  Purchase #3 $185.30   8.114%   $200.3352   $200.34   $200.35   $200.30  
  Purchase #4 $85.61   11.351%   $95.3276   $95.33   $95.35   $95.30  
  Purchase #5 $120.85   11.766%   $135.0692   $135.07   $135.05   $135.10  
  Purchase #6 $244.41   3.667%   $253.3725   $253.37   $253.35   $253.40  
  Purchase #7 $89.28   10.173%   $98.3625   $98.36   $98.35   $98.40  
  7 purchase totals = $1,104.58       $1,202.3242   $1,202.32   $1,202.30   $1,202.40