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 $63.36   13.560%   $71.9516   $71.95   $71.95   $72.00  
  Purchase #2 $232.79   5.473%   $245.5306   $245.53   $245.55   $245.50  
  Purchase #3 $49.80   3.703%   $51.6441   $51.64   $51.65   $51.60  
  Purchase #4 $88.27   11.167%   $98.1271   $98.13   $98.15   $98.10  
  Purchase #5 $180.56   13.795%   $205.4683   $205.47   $205.45   $205.50  
  Purchase #6 $139.52   13.608%   $158.5059   $158.51   $158.50   $158.50  
  Purchase #7 $70.65   7.754%   $76.1282   $76.13   $76.15   $76.10  
  7 purchase totals = $824.95       $907.3558   $907.36   $907.40   $907.30