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 $111.37   5.732%   $117.7537   $117.75   $117.75   $117.80  
  Purchase #2 $226.26   11.776%   $252.9044   $252.90   $252.90   $252.90  
  Purchase #3 $158.83   11.872%   $177.6863   $177.69   $177.70   $177.70  
  Purchase #4 $245.96   9.390%   $269.0556   $269.06   $269.05   $269.10  
  Purchase #5 $246.92   4.203%   $257.298   $257.30   $257.30   $257.30  
  Purchase #6 $174.63   11.609%   $194.9028   $194.90   $194.90   $194.90  
  Purchase #7 $163.49   8.339%   $177.1234   $177.12   $177.10   $177.10  
  7 purchase totals = $1,327.46       $1,446.7242   $1,446.72   $1,446.70   $1,446.80