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 $141.65   8.457%   $153.6293   $153.63   $153.65   $153.60  
  Purchase #2 $229.83   9.453%   $251.5558   $251.56   $251.55   $251.60  
  Purchase #3 $30.99   7.667%   $33.366   $33.37   $33.35   $33.40  
  Purchase #4 $215.27   7.807%   $232.0761   $232.08   $232.10   $232.10  
  Purchase #5 $117.91   7.832%   $127.1447   $127.14   $127.15   $127.10  
  Purchase #6 $143.36   9.674%   $157.2286   $157.23   $157.25   $157.20  
  Purchase #7 $184.99   11.199%   $205.707   $205.71   $205.70   $205.70  
  7 purchase totals = $1,064.00       $1,160.7075   $1,160.72   $1,160.75   $1,160.70