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 $193.99   7.221%   $207.998   $208.00   $208.00   $208.00  
  Purchase #2 $205.60   8.449%   $222.9711   $222.97   $222.95   $223.00  
  Purchase #3 $197.77   8.409%   $214.4005   $214.40   $214.40   $214.40  
  Purchase #4 $216.30   6.813%   $231.0365   $231.04   $231.05   $231.00  
  Purchase #5 $71.39   5.236%   $75.128   $75.13   $75.15   $75.10  
  Purchase #6 $250.26   7.482%   $268.9845   $268.98   $269.00   $269.00  
  Purchase #7 $128.28   12.111%   $143.816   $143.82   $143.80   $143.80  
  7 purchase totals = $1,263.59       $1,364.3346   $1,364.34   $1,364.35   $1,364.30