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 $84.39   13.462%   $95.7506   $95.75   $95.75   $95.80  
  Purchase #2 $73.70   5.262%   $77.5781   $77.58   $77.60   $77.60  
  Purchase #3 $11.65   13.823%   $13.2604   $13.26   $13.25   $13.30  
  Purchase #4 $94.40   11.666%   $105.4127   $105.41   $105.40   $105.40  
  Purchase #5 $138.72   7.141%   $148.626   $148.63   $148.65   $148.60  
  Purchase #6 $58.88   12.231%   $66.0816   $66.08   $66.10   $66.10  
  Purchase #7 $219.97   4.118%   $229.0284   $229.03   $229.05   $229.00  
  7 purchase totals = $681.71       $735.7378   $735.74   $735.80   $735.80