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 $106.27   6.767%   $113.4613   $113.46   $113.45   $113.50  
  Purchase #2 $119.36   11.188%   $132.714   $132.71   $132.70   $132.70  
  Purchase #3 $51.29   3.541%   $53.1062   $53.11   $53.10   $53.10  
  Purchase #4 $24.85   3.732%   $25.7774   $25.78   $25.80   $25.80  
  Purchase #5 $232.28   10.326%   $256.2652   $256.27   $256.25   $256.30  
  Purchase #6 $237.55   13.288%   $269.1156   $269.12   $269.10   $269.10  
  Purchase #7 $226.95   9.612%   $248.7644   $248.76   $248.75   $248.80  
  7 purchase totals = $998.55       $1,099.2041   $1,099.21   $1,099.15   $1,099.30