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 $63.29   13.459%   $71.8082   $71.81   $71.80   $71.80  
  Purchase #2 $74.34   11.262%   $82.7122   $82.71   $82.70   $82.70  
  Purchase #3 $244.97   3.646%   $253.9016   $253.90   $253.90   $253.90  
  Purchase #4 $109.54   5.113%   $115.1408   $115.14   $115.15   $115.10  
  Purchase #5 $87.55   5.844%   $92.6664   $92.67   $92.65   $92.70  
  Purchase #6 $247.31   4.109%   $257.472   $257.47   $257.45   $257.50  
  Purchase #7 $248.57   9.715%   $272.7186   $272.72   $272.70   $272.70  
  7 purchase totals = $1,075.57       $1,146.4198   $1,146.42   $1,146.35   $1,146.40