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 $110.37   13.495%   $125.2644   $125.26   $125.25   $125.30  
  Purchase #2 $201.32   6.119%   $213.6388   $213.64   $213.65   $213.60  
  Purchase #3 $167.91   12.169%   $188.343   $188.34   $188.35   $188.30  
  Purchase #4 $48.83   12.612%   $54.9884   $54.99   $55.00   $55.00  
  Purchase #5 $195.90   11.360%   $218.1542   $218.15   $218.15   $218.20  
  Purchase #6 $181.63   10.168%   $200.0981   $200.10   $200.10   $200.10  
  Purchase #7 $10.61   3.173%   $10.9467   $10.95   $10.95   $10.90  
  7 purchase totals = $916.57       $1,011.4336   $1,011.43   $1,011.45   $1,011.40