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 $86.98   11.815%   $97.2567   $97.26   $97.25   $97.30  
  Purchase #2 $66.51   4.866%   $69.7464   $69.75   $69.75   $69.70  
  Purchase #3 $149.69   4.578%   $156.5428   $156.54   $156.55   $156.50  
  Purchase #4 $136.90   9.785%   $150.2957   $150.30   $150.30   $150.30  
  Purchase #5 $83.83   11.705%   $93.6423   $93.64   $93.65   $93.60  
  Purchase #6 $101.28   6.113%   $107.4712   $107.47   $107.45   $107.50  
  Purchase #7 $46.52   3.354%   $48.0803   $48.08   $48.10   $48.10  
  7 purchase totals = $671.71       $723.0354   $723.04   $723.05   $723.00