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 $206.69   9.402%   $226.123   $226.12   $226.10   $226.10  
  Purchase #2 $86.82   11.176%   $96.523   $96.52   $96.50   $96.50  
  Purchase #3 $111.83   12.869%   $126.2214   $126.22   $126.20   $126.20  
  Purchase #4 $235.73   10.209%   $259.7957   $259.80   $259.80   $259.80  
  Purchase #5 $195.26   9.738%   $214.2744   $214.27   $214.25   $214.30  
  Purchase #6 $175.94   5.202%   $185.0924   $185.09   $185.10   $185.10  
  Purchase #7 $241.93   7.548%   $260.1909   $260.19   $260.20   $260.20  
  7 purchase totals = $1,254.20       $1,368.2208   $1,368.21   $1,368.15   $1,368.20