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 $96.65   10.206%   $106.5141   $106.51   $106.50   $106.50  
  Purchase #2 $205.69   10.248%   $226.7691   $226.77   $226.75   $226.80  
  Purchase #3 $86.52   11.643%   $96.5935   $96.59   $96.60   $96.60  
  Purchase #4 $176.92   9.293%   $193.3612   $193.36   $193.35   $193.40  
  Purchase #5 $35.40   3.364%   $36.5909   $36.59   $36.60   $36.60  
  Purchase #6 $246.51   11.157%   $274.0131   $274.01   $274.00   $274.00  
  Purchase #7 $186.68   8.509%   $202.5646   $202.56   $202.55   $202.60  
  7 purchase totals = $1,034.37       $1,136.4065   $1,136.39   $1,136.35   $1,136.50