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 $158.89   9.190%   $173.492   $173.49   $173.50   $173.50  
  Purchase #2 $180.70   3.631%   $187.2612   $187.26   $187.25   $187.30  
  Purchase #3 $193.34   6.739%   $206.3692   $206.37   $206.35   $206.40  
  Purchase #4 $64.94   3.750%   $67.3753   $67.38   $67.40   $67.40  
  Purchase #5 $114.65   3.135%   $118.2443   $118.24   $118.25   $118.20  
  Purchase #6 $119.53   6.780%   $127.6341   $127.63   $127.65   $127.60  
  Purchase #7 $127.32   5.370%   $134.1571   $134.16   $134.15   $134.20  
  7 purchase totals = $959.37       $1,014.5332   $1,014.53   $1,014.55   $1,014.60