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 $190.36   12.853%   $214.827   $214.83   $214.85   $214.80  
  Purchase #2 $194.99   5.292%   $205.3089   $205.31   $205.30   $205.30  
  Purchase #3 $217.87   11.283%   $242.4523   $242.45   $242.45   $242.50  
  Purchase #4 $64.92   8.565%   $70.4804   $70.48   $70.50   $70.50  
  Purchase #5 $26.87   9.149%   $29.3283   $29.33   $29.35   $29.30  
  Purchase #6 $202.71   11.719%   $226.4656   $226.47   $226.45   $226.50  
  Purchase #7 $98.63   8.232%   $106.7492   $106.75   $106.75   $106.70  
  7 purchase totals = $996.35       $1,095.6117   $1,095.62   $1,095.65   $1,095.60