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 $62.88   9.673%   $68.9624   $68.96   $68.95   $69.00  
  Purchase #2 $98.50   3.295%   $101.7456   $101.75   $101.75   $101.70  
  Purchase #3 $150.26   7.482%   $161.5025   $161.50   $161.50   $161.50  
  Purchase #4 $107.69   4.249%   $112.2657   $112.27   $112.25   $112.30  
  Purchase #5 $233.63   12.417%   $262.6398   $262.64   $262.65   $262.60  
  Purchase #6 $69.27   9.546%   $75.8825   $75.88   $75.90   $75.90  
  Purchase #7 $219.59   4.202%   $228.8172   $228.82   $228.80   $228.80  
  7 purchase totals = $941.82       $1,011.8157   $1,011.82   $1,011.80   $1,011.80