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 $158.59   6.535%   $168.9539   $168.95   $168.95   $169.00  
  Purchase #2 $183.66   3.256%   $189.64   $189.64   $189.65   $189.60  
  Purchase #3 $153.84   13.219%   $174.1761   $174.18   $174.20   $174.20  
  Purchase #4 $74.83   13.547%   $84.9672   $84.97   $84.95   $85.00  
  Purchase #5 $208.97   12.758%   $235.6304   $235.63   $235.65   $235.60  
  Purchase #6 $94.92   8.463%   $102.9531   $102.95   $102.95   $103.00  
  Purchase #7 $90.38   4.667%   $94.598   $94.60   $94.60   $94.60  
  7 purchase totals = $965.19       $1,050.9187   $1,050.92   $1,050.95   $1,051.00