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 $246.28   5.633%   $260.153   $260.15   $260.15   $260.20  
  Purchase #2 $127.25   5.391%   $134.11   $134.11   $134.10   $134.10  
  Purchase #3 $59.72   5.479%   $62.9921   $62.99   $63.00   $63.00  
  Purchase #4 $228.80   4.361%   $238.778   $238.78   $238.80   $238.80  
  Purchase #5 $7.79   8.721%   $8.4694   $8.47   $8.45   $8.50  
  Purchase #6 $127.89   10.411%   $141.2046   $141.20   $141.20   $141.20  
  Purchase #7 $208.77   7.869%   $225.1981   $225.20   $225.20   $225.20  
  7 purchase totals = $1,006.50       $1,070.9052   $1,070.90   $1,070.90   $1,071.00