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 $216.58   8.839%   $235.7235   $235.72   $235.70   $235.70  
  Purchase #2 $150.80   4.448%   $157.5076   $157.51   $157.50   $157.50  
  Purchase #3 $101.40   4.684%   $106.1496   $106.15   $106.15   $106.10  
  Purchase #4 $53.36   12.381%   $59.9665   $59.97   $59.95   $60.00  
  Purchase #5 $188.65   8.764%   $205.1833   $205.18   $205.20   $205.20  
  Purchase #6 $228.63   3.223%   $235.9987   $236.00   $236.00   $236.00  
  Purchase #7 $123.64   9.795%   $135.7505   $135.75   $135.75   $135.80  
  7 purchase totals = $1,063.06       $1,136.2797   $1,136.28   $1,136.25   $1,136.30