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 $23.27   9.523%   $25.486   $25.49   $25.50   $25.50  
  Purchase #2 $239.57   9.442%   $262.1902   $262.19   $262.20   $262.20  
  Purchase #3 $92.57   5.713%   $97.8585   $97.86   $97.85   $97.90  
  Purchase #4 $144.56   3.236%   $149.238   $149.24   $149.25   $149.20  
  Purchase #5 $161.69   7.253%   $173.4174   $173.42   $173.40   $173.40  
  Purchase #6 $167.27   4.771%   $175.2505   $175.25   $175.25   $175.30  
  Purchase #7 $138.33   7.851%   $149.1903   $149.19   $149.20   $149.20  
  7 purchase totals = $967.26       $1,032.6309   $1,032.64   $1,032.65   $1,032.70