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 $69.27   5.501%   $73.0805   $73.08   $73.10   $73.10  
  Purchase #2 $113.52   5.319%   $119.5581   $119.56   $119.55   $119.60  
  Purchase #3 $141.37   8.288%   $153.0867   $153.09   $153.10   $153.10  
  Purchase #4 $197.36   8.646%   $214.4237   $214.42   $214.40   $214.40  
  Purchase #5 $143.75   9.627%   $157.5888   $157.59   $157.60   $157.60  
  Purchase #6 $192.71   9.832%   $211.6572   $211.66   $211.65   $211.70  
  Purchase #7 $130.27   5.685%   $137.6758   $137.68   $137.70   $137.70  
  7 purchase totals = $988.25       $1,067.0708   $1,067.08   $1,067.10   $1,067.20