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 $154.47   5.847%   $163.5019   $163.50   $163.50   $163.50  
  Purchase #2 $237.48   5.770%   $251.1826   $251.18   $251.20   $251.20  
  Purchase #3 $56.73   5.299%   $59.7361   $59.74   $59.75   $59.70  
  Purchase #4 $24.80   7.479%   $26.6548   $26.65   $26.65   $26.70  
  Purchase #5 $175.93   8.693%   $191.2236   $191.22   $191.20   $191.20  
  Purchase #6 $229.66   12.550%   $258.4823   $258.48   $258.50   $258.50  
  Purchase #7 $177.55   12.803%   $200.2817   $200.28   $200.30   $200.30  
  7 purchase totals = $1,056.62       $1,151.0630   $1,151.05   $1,151.10   $1,151.10