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 $214.54   8.677%   $233.1556   $233.16   $233.15   $233.20  
  Purchase #2 $192.86   4.223%   $201.0045   $201.00   $201.00   $201.00  
  Purchase #3 $122.42   8.540%   $132.8747   $132.87   $132.85   $132.90  
  Purchase #4 $50.77   7.460%   $54.5574   $54.56   $54.55   $54.60  
  Purchase #5 $223.47   4.832%   $234.2681   $234.27   $234.25   $234.30  
  Purchase #6 $61.31   6.608%   $65.3614   $65.36   $65.35   $65.40  
  Purchase #7 $182.37   6.591%   $194.39   $194.39   $194.40   $194.40  
  7 purchase totals = $1,047.74       $1,115.6117   $1,115.61   $1,115.55   $1,115.80