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 $119.61   6.722%   $127.6502   $127.65   $127.65   $127.70  
  Purchase #2 $250.74   7.718%   $270.0921   $270.09   $270.10   $270.10  
  Purchase #3 $36.74   13.508%   $41.7028   $41.70   $41.70   $41.70  
  Purchase #4 $244.70   6.231%   $259.9473   $259.95   $259.95   $259.90  
  Purchase #5 $96.92   8.760%   $105.4102   $105.41   $105.40   $105.40  
  Purchase #6 $238.74   6.338%   $253.8713   $253.87   $253.85   $253.90  
  Purchase #7 $5.67   3.762%   $5.8833   $5.88   $5.90   $5.90  
  7 purchase totals = $993.12       $1,064.5572   $1,064.55   $1,064.55   $1,064.60