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 $175.69   9.807%   $192.9199   $192.92   $192.90   $192.90  
  Purchase #2 $94.89   12.434%   $106.6886   $106.69   $106.70   $106.70  
  Purchase #3 $87.95   9.683%   $96.4662   $96.47   $96.45   $96.50  
  Purchase #4 $162.83   5.220%   $171.3297   $171.33   $171.35   $171.30  
  Purchase #5 $29.32   11.247%   $32.6176   $32.62   $32.60   $32.60  
  Purchase #6 $218.65   3.775%   $226.904   $226.90   $226.90   $226.90  
  Purchase #7 $196.84   12.447%   $221.3407   $221.34   $221.35   $221.30  
  7 purchase totals = $966.17       $1,048.2667   $1,048.27   $1,048.25   $1,048.20