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 $86.63   13.732%   $98.526   $98.53   $98.55   $98.50  
  Purchase #2 $119.52   5.620%   $126.237   $126.24   $126.25   $126.20  
  Purchase #3 $124.60   9.190%   $136.0507   $136.05   $136.05   $136.10  
  Purchase #4 $30.25   13.733%   $34.4042   $34.40   $34.40   $34.40  
  Purchase #5 $204.96   12.312%   $230.1947   $230.19   $230.20   $230.20  
  Purchase #6 $71.91   13.150%   $81.3662   $81.37   $81.35   $81.40  
  Purchase #7 $81.25   5.185%   $85.4628   $85.46   $85.45   $85.50  
  7 purchase totals = $719.12       $792.2416   $792.24   $792.25   $792.30