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 $89.50   6.420%   $95.2459   $95.25   $95.25   $95.20  
  Purchase #2 $69.34   11.186%   $77.0964   $77.10   $77.10   $77.10  
  Purchase #3 $236.98   7.433%   $254.5947   $254.59   $254.60   $254.60  
  Purchase #4 $243.29   4.738%   $254.8171   $254.82   $254.80   $254.80  
  Purchase #5 $107.85   8.623%   $117.1499   $117.15   $117.15   $117.10  
  Purchase #6 $169.33   10.652%   $187.367   $187.37   $187.35   $187.40  
  Purchase #7 $74.75   11.652%   $83.4599   $83.46   $83.45   $83.50  
  7 purchase totals = $991.04       $1,069.7309   $1,069.74   $1,069.70   $1,069.70