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 $65.84   13.832%   $74.947   $74.95   $74.95   $74.90  
  Purchase #2 $132.68   10.829%   $147.0479   $147.05   $147.05   $147.00  
  Purchase #3 $14.46   12.446%   $16.2597   $16.26   $16.25   $16.30  
  Purchase #4 $77.37   11.826%   $86.5198   $86.52   $86.50   $86.50  
  Purchase #5 $9.81   12.437%   $11.0301   $11.03   $11.05   $11.00  
  Purchase #6 $106.84   12.818%   $120.5348   $120.53   $120.55   $120.50  
  Purchase #7 $32.33   10.260%   $35.6471   $35.65   $35.65   $35.60  
  7 purchase totals = $439.33       $491.9864   $491.99   $492.00   $491.80