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 $243.26   13.465%   $276.015   $276.02   $276.00   $276.00  
  Purchase #2 $88.35   12.848%   $99.7012   $99.70   $99.70   $99.70  
  Purchase #3 $9.96   4.385%   $10.3967   $10.40   $10.40   $10.40  
  Purchase #4 $144.94   8.642%   $157.4657   $157.47   $157.45   $157.50  
  Purchase #5 $162.76   8.259%   $176.2023   $176.20   $176.20   $176.20  
  Purchase #6 $82.76   4.500%   $86.4842   $86.48   $86.50   $86.50  
  Purchase #7 $190.91   9.288%   $208.6417   $208.64   $208.65   $208.60  
  7 purchase totals = $922.94       $1,014.9068   $1,014.91   $1,014.90   $1,014.90