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 $176.48   9.273%   $192.845   $192.85   $192.85   $192.80  
  Purchase #2 $200.69   13.459%   $227.7009   $227.70   $227.70   $227.70  
  Purchase #3 $198.80   7.807%   $214.3203   $214.32   $214.30   $214.30  
  Purchase #4 $124.25   10.732%   $137.5845   $137.58   $137.60   $137.60  
  Purchase #5 $121.60   11.580%   $135.6813   $135.68   $135.70   $135.70  
  Purchase #6 $23.98   6.539%   $25.5481   $25.55   $25.55   $25.50  
  Purchase #7 $224.36   10.670%   $248.2992   $248.30   $248.30   $248.30  
  7 purchase totals = $1,070.16       $1,181.9793   $1,181.98   $1,182.00   $1,181.90