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 $96.65   11.253%   $107.526   $107.53   $107.55   $107.50  
  Purchase #2 $163.46   8.464%   $177.2953   $177.30   $177.30   $177.30  
  Purchase #3 $108.47   10.538%   $119.9006   $119.90   $119.90   $119.90  
  Purchase #4 $248.57   8.258%   $269.0969   $269.10   $269.10   $269.10  
  Purchase #5 $141.99   11.352%   $158.1087   $158.11   $158.10   $158.10  
  Purchase #6 $118.48   5.689%   $125.2203   $125.22   $125.20   $125.20  
  Purchase #7 $97.37   5.410%   $102.6377   $102.64   $102.65   $102.60  
  7 purchase totals = $974.99       $1,059.7855   $1,059.80   $1,059.80   $1,059.70