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 $204.30   4.266%   $213.0154   $213.02   $213.00   $213.00  
  Purchase #2 $227.99   6.739%   $243.3542   $243.35   $243.35   $243.40  
  Purchase #3 $232.99   9.305%   $254.6697   $254.67   $254.65   $254.70  
  Purchase #4 $64.52   8.235%   $69.8332   $69.83   $69.85   $69.80  
  Purchase #5 $164.80   11.135%   $183.1505   $183.15   $183.15   $183.20  
  Purchase #6 $195.26   3.236%   $201.5786   $201.58   $201.60   $201.60  
  Purchase #7 $207.78   3.864%   $215.8086   $215.81   $215.80   $215.80  
  7 purchase totals = $1,297.64       $1,381.4102   $1,381.41   $1,381.40   $1,381.50