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 $56.73   9.214%   $61.9571   $61.96   $61.95   $62.00  
  Purchase #2 $216.57   9.490%   $237.1225   $237.12   $237.10   $237.10  
  Purchase #3 $161.76   13.323%   $183.3113   $183.31   $183.30   $183.30  
  Purchase #4 $183.82   11.124%   $204.2681   $204.27   $204.25   $204.30  
  Purchase #5 $44.36   4.122%   $46.1885   $46.19   $46.20   $46.20  
  Purchase #6 $184.71   11.324%   $205.6266   $205.63   $205.65   $205.60  
  Purchase #7 $61.94   12.466%   $69.6614   $69.66   $69.65   $69.70  
  7 purchase totals = $909.89       $1,008.1355   $1,008.14   $1,008.10   $1,008.20