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 $13.92   4.836%   $14.5932   $14.59   $14.60   $14.60  
  Purchase #2 $182.55   10.234%   $201.2322   $201.23   $201.25   $201.20  
  Purchase #3 $245.94   9.563%   $269.4592   $269.46   $269.45   $269.50  
  Purchase #4 $206.74   12.814%   $233.2317   $233.23   $233.25   $233.20  
  Purchase #5 $69.86   10.240%   $77.0137   $77.01   $77.00   $77.00  
  Purchase #6 $191.77   5.625%   $202.5571   $202.56   $202.55   $202.60  
  Purchase #7 $213.37   11.622%   $238.1679   $238.17   $238.15   $238.20  
  7 purchase totals = $1,124.15       $1,236.2550   $1,236.25   $1,236.25   $1,236.30