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 $58.68   7.320%   $62.9754   $62.98   $63.00   $63.00  
  Purchase #2 $118.91   7.335%   $127.632   $127.63   $127.65   $127.60  
  Purchase #3 $210.96   11.844%   $235.9461   $235.95   $235.95   $235.90  
  Purchase #4 $216.33   11.731%   $241.7077   $241.71   $241.70   $241.70  
  Purchase #5 $135.71   4.135%   $141.3216   $141.32   $141.30   $141.30  
  Purchase #6 $12.86   8.324%   $13.9305   $13.93   $13.95   $13.90  
  Purchase #7 $186.70   10.417%   $206.1485   $206.15   $206.15   $206.10  
  7 purchase totals = $940.15       $1,029.6618   $1,029.67   $1,029.70   $1,029.50