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 $179.72   3.797%   $186.544   $186.54   $186.55   $186.50  
  Purchase #2 $182.55   8.153%   $197.4333   $197.43   $197.45   $197.40  
  Purchase #3 $84.93   8.589%   $92.2246   $92.22   $92.20   $92.20  
  Purchase #4 $65.46   6.272%   $69.5657   $69.57   $69.55   $69.60  
  Purchase #5 $197.91   13.346%   $224.3231   $224.32   $224.30   $224.30  
  Purchase #6 $167.80   10.173%   $184.8703   $184.87   $184.85   $184.90  
  Purchase #7 $133.41   5.212%   $140.3633   $140.36   $140.35   $140.40  
  7 purchase totals = $1,011.78       $1,095.3243   $1,095.31   $1,095.25   $1,095.30