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 $119.46   4.644%   $125.0077   $125.01   $125.00   $125.00  
  Purchase #2 $27.40   10.215%   $30.1989   $30.20   $30.20   $30.20  
  Purchase #3 $56.34   10.183%   $62.0771   $62.08   $62.10   $62.10  
  Purchase #4 $41.91   8.493%   $45.4694   $45.47   $45.45   $45.50  
  Purchase #5 $172.34   7.239%   $184.8157   $184.82   $184.80   $184.80  
  Purchase #6 $97.52   13.828%   $111.0051   $111.01   $111.00   $111.00  
  Purchase #7 $121.68   13.792%   $138.4621   $138.46   $138.45   $138.50  
  7 purchase totals = $636.65       $697.0360   $697.05   $697.00   $697.10