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 $214.63   5.468%   $226.366   $226.37   $226.35   $226.40  
  Purchase #2 $202.82   12.258%   $227.6817   $227.68   $227.70   $227.70  
  Purchase #3 $225.65   12.486%   $253.8247   $253.82   $253.80   $253.80  
  Purchase #4 $247.66   8.248%   $268.087   $268.09   $268.10   $268.10  
  Purchase #5 $246.48   10.532%   $272.4393   $272.44   $272.45   $272.40  
  Purchase #6 $165.25   9.554%   $181.038   $181.04   $181.05   $181.00  
  Purchase #7 $181.48   12.253%   $203.7167   $203.72   $203.70   $203.70  
  7 purchase totals = $1,483.97       $1,633.1534   $1,633.16   $1,633.15   $1,633.10