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 $228.27   7.441%   $245.2556   $245.26   $245.25   $245.30  
  Purchase #2 $221.59   9.104%   $241.7636   $241.76   $241.75   $241.80  
  Purchase #3 $197.36   4.873%   $206.9774   $206.98   $207.00   $207.00  
  Purchase #4 $79.54   3.707%   $82.4885   $82.49   $82.50   $82.50  
  Purchase #5 $50.86   13.188%   $57.5674   $57.57   $57.55   $57.60  
  Purchase #6 $17.99   3.816%   $18.6765   $18.68   $18.70   $18.70  
  Purchase #7 $229.61   9.731%   $251.9533   $251.95   $251.95   $252.00  
  7 purchase totals = $1,025.22       $1,104.6823   $1,104.69   $1,104.70   $1,104.90