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 $112.93   12.469%   $127.0112   $127.01   $127.00   $127.00  
  Purchase #2 $248.88   10.756%   $275.6495   $275.65   $275.65   $275.60  
  Purchase #3 $88.92   8.715%   $96.6694   $96.67   $96.65   $96.70  
  Purchase #4 $24.59   5.856%   $26.03   $26.03   $26.05   $26.00  
  Purchase #5 $247.71   10.650%   $274.0911   $274.09   $274.10   $274.10  
  Purchase #6 $150.52   12.255%   $168.9662   $168.97   $168.95   $169.00  
  Purchase #7 $158.80   4.831%   $166.4716   $166.47   $166.45   $166.50  
  7 purchase totals = $1,032.35       $1,134.8890   $1,134.89   $1,134.85   $1,134.90