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 $62.69   8.621%   $68.0945   $68.09   $68.10   $68.10  
  Purchase #2 $192.81   6.760%   $205.844   $205.84   $205.85   $205.80  
  Purchase #3 $153.69   3.870%   $159.6378   $159.64   $159.65   $159.60  
  Purchase #4 $200.68   5.594%   $211.906   $211.91   $211.90   $211.90  
  Purchase #5 $117.76   3.719%   $122.1395   $122.14   $122.15   $122.10  
  Purchase #6 $239.50   11.363%   $266.7144   $266.71   $266.70   $266.70  
  Purchase #7 $123.53   9.429%   $135.1776   $135.18   $135.20   $135.20  
  7 purchase totals = $1,090.66       $1,169.5138   $1,169.51   $1,169.55   $1,169.40