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 $34.26   5.258%   $36.0614   $36.06   $36.05   $36.10  
  Purchase #2 $230.84   10.188%   $254.358   $254.36   $254.35   $254.40  
  Purchase #3 $27.54   10.594%   $30.4576   $30.46   $30.45   $30.50  
  Purchase #4 $87.66   5.678%   $92.6373   $92.64   $92.65   $92.60  
  Purchase #5 $178.85   4.760%   $187.3633   $187.36   $187.35   $187.40  
  Purchase #6 $95.33   3.511%   $98.677   $98.68   $98.70   $98.70  
  Purchase #7 $23.90   11.163%   $26.568   $26.57   $26.55   $26.60  
  7 purchase totals = $678.38       $726.1226   $726.13   $726.10   $726.30