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 $152.58   10.732%   $168.9549   $168.95   $168.95   $169.00  
  Purchase #2 $124.49   9.594%   $136.4336   $136.43   $136.45   $136.40  
  Purchase #3 $236.87   10.613%   $262.009   $262.01   $262.00   $262.00  
  Purchase #4 $197.96   3.801%   $205.4845   $205.48   $205.50   $205.50  
  Purchase #5 $62.57   12.679%   $70.5033   $70.50   $70.50   $70.50  
  Purchase #6 $31.57   8.235%   $34.1698   $34.17   $34.15   $34.20  
  Purchase #7 $126.97   5.751%   $134.272   $134.27   $134.25   $134.30  
  7 purchase totals = $933.01       $1,011.8271   $1,011.81   $1,011.80   $1,011.90