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 $92.44   5.662%   $97.674   $97.67   $97.65   $97.70  
  Purchase #2 $180.74   8.210%   $195.5788   $195.58   $195.60   $195.60  
  Purchase #3 $78.38   10.752%   $86.8074   $86.81   $86.80   $86.80  
  Purchase #4 $75.59   7.620%   $81.35   $81.35   $81.35   $81.40  
  Purchase #5 $161.96   4.361%   $169.0231   $169.02   $169.00   $169.00  
  Purchase #6 $177.78   6.536%   $189.3997   $189.40   $189.40   $189.40  
  Purchase #7 $187.25   13.546%   $212.6149   $212.61   $212.60   $212.60  
  7 purchase totals = $954.14       $1,032.4479   $1,032.44   $1,032.40   $1,032.50