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 $23.71   5.267%   $24.9588   $24.96   $24.95   $25.00  
  Purchase #2 $73.62   9.498%   $80.6124   $80.61   $80.60   $80.60  
  Purchase #3 $31.26   12.472%   $35.1587   $35.16   $35.15   $35.20  
  Purchase #4 $30.94   10.853%   $34.2979   $34.30   $34.30   $34.30  
  Purchase #5 $72.50   5.546%   $76.5209   $76.52   $76.50   $76.50  
  Purchase #6 $97.33   10.117%   $107.1769   $107.18   $107.20   $107.20  
  Purchase #7 $95.87   7.493%   $103.0535   $103.05   $103.05   $103.10  
  7 purchase totals = $425.23       $461.7791   $461.78   $461.75   $461.90