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 $194.95   10.821%   $216.0455   $216.05   $216.05   $216.00  
  Purchase #2 $177.30   13.108%   $200.5405   $200.54   $200.55   $200.50  
  Purchase #3 $168.28   6.763%   $179.6608   $179.66   $179.65   $179.70  
  Purchase #4 $159.70   13.598%   $181.416   $181.42   $181.40   $181.40  
  Purchase #5 $27.44   5.759%   $29.0203   $29.02   $29.00   $29.00  
  Purchase #6 $200.56   4.466%   $209.517   $209.52   $209.50   $209.50  
  Purchase #7 $180.87   4.526%   $189.0562   $189.06   $189.05   $189.10  
  7 purchase totals = $1,109.10       $1,205.2563   $1,205.27   $1,205.20   $1,205.20