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 $94.33   13.371%   $106.9429   $106.94   $106.95   $106.90  
  Purchase #2 $153.54   4.643%   $160.6689   $160.67   $160.65   $160.70  
  Purchase #3 $208.63   4.576%   $218.1769   $218.18   $218.20   $218.20  
  Purchase #4 $223.96   3.180%   $231.0819   $231.08   $231.10   $231.10  
  Purchase #5 $41.53   12.832%   $46.8591   $46.86   $46.85   $46.90  
  Purchase #6 $146.30   11.527%   $163.164   $163.16   $163.15   $163.20  
  Purchase #7 $118.52   10.130%   $130.5261   $130.53   $130.55   $130.50  
  7 purchase totals = $986.81       $1,057.4198   $1,057.42   $1,057.45   $1,057.50