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 $161.43   9.371%   $176.5576   $176.56   $176.55   $176.60  
  Purchase #2 $87.88   11.491%   $97.9783   $97.98   $98.00   $98.00  
  Purchase #3 $18.58   9.329%   $20.3133   $20.31   $20.30   $20.30  
  Purchase #4 $154.74   5.392%   $163.0836   $163.08   $163.10   $163.10  
  Purchase #5 $159.58   10.821%   $176.8482   $176.85   $176.85   $176.80  
  Purchase #6 $186.73   8.754%   $203.0763   $203.08   $203.10   $203.10  
  Purchase #7 $177.53   10.680%   $196.4902   $196.49   $196.50   $196.50  
  7 purchase totals = $946.47       $1,034.3475   $1,034.35   $1,034.40   $1,034.40