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 $242.54   10.500%   $268.0067   $268.01   $268.00   $268.00  
  Purchase #2 $234.27   8.338%   $253.8034   $253.80   $253.80   $253.80  
  Purchase #3 $162.81   11.709%   $181.8734   $181.87   $181.85   $181.90  
  Purchase #4 $80.53   9.494%   $88.1755   $88.18   $88.20   $88.20  
  Purchase #5 $245.85   10.693%   $272.1387   $272.14   $272.15   $272.10  
  Purchase #6 $65.30   11.136%   $72.5718   $72.57   $72.55   $72.60  
  Purchase #7 $28.58   7.405%   $30.6963   $30.70   $30.70   $30.70  
  7 purchase totals = $1,059.88       $1,167.2658   $1,167.27   $1,167.25   $1,167.30