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 $177.30   11.650%   $197.9555   $197.96   $197.95   $198.00  
  Purchase #2 $213.59   8.453%   $231.6448   $231.64   $231.65   $231.60  
  Purchase #3 $206.76   7.711%   $222.7033   $222.70   $222.70   $222.70  
  Purchase #4 $118.67   3.622%   $122.9682   $122.97   $122.95   $123.00  
  Purchase #5 $231.55   8.691%   $251.674   $251.67   $251.65   $251.70  
  Purchase #6 $186.95   7.153%   $200.3225   $200.32   $200.30   $200.30  
  Purchase #7 $147.55   5.277%   $155.3362   $155.34   $155.35   $155.30  
  7 purchase totals = $1,282.37       $1,382.6045   $1,382.60   $1,382.55   $1,382.60