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 $54.68   13.293%   $61.9486   $61.95   $61.95   $61.90  
  Purchase #2 $134.53   9.866%   $147.8027   $147.80   $147.80   $147.80  
  Purchase #3 $244.42   3.200%   $252.2414   $252.24   $252.25   $252.20  
  Purchase #4 $214.90   7.766%   $231.5891   $231.59   $231.60   $231.60  
  Purchase #5 $194.53   10.713%   $215.37   $215.37   $215.35   $215.40  
  Purchase #6 $55.28   7.590%   $59.4758   $59.48   $59.50   $59.50  
  Purchase #7 $192.66   10.131%   $212.1784   $212.18   $212.20   $212.20  
  7 purchase totals = $1,091.00       $1,180.6060   $1,180.61   $1,180.65   $1,180.60