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 $214.53   8.716%   $233.2284   $233.23   $233.25   $233.20  
  Purchase #2 $134.37   9.493%   $147.1257   $147.13   $147.15   $147.10  
  Purchase #3 $167.37   5.342%   $176.3109   $176.31   $176.30   $176.30  
  Purchase #4 $239.41   6.379%   $254.682   $254.68   $254.70   $254.70  
  Purchase #5 $149.25   6.564%   $159.0468   $159.05   $159.05   $159.00  
  Purchase #6 $176.54   8.411%   $191.3888   $191.39   $191.40   $191.40  
  Purchase #7 $195.92   3.343%   $202.4696   $202.47   $202.45   $202.50  
  7 purchase totals = $1,277.39       $1,364.2522   $1,364.26   $1,364.30   $1,364.20