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 $43.81   5.648%   $46.2844   $46.28   $46.30   $46.30  
  Purchase #2 $229.81   5.151%   $241.6475   $241.65   $241.65   $241.60  
  Purchase #3 $13.58   3.462%   $14.0501   $14.05   $14.05   $14.10  
  Purchase #4 $85.94   5.215%   $90.4218   $90.42   $90.40   $90.40  
  Purchase #5 $47.64   5.732%   $50.3707   $50.37   $50.35   $50.40  
  Purchase #6 $165.66   7.157%   $177.5163   $177.52   $177.50   $177.50  
  Purchase #7 $133.41   12.727%   $150.3891   $150.39   $150.40   $150.40  
  7 purchase totals = $719.85       $770.6799   $770.68   $770.65   $770.70