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 $46.50   13.160%   $52.6194   $52.62   $52.60   $52.60  
  Purchase #2 $122.98   7.512%   $132.2183   $132.22   $132.20   $132.20  
  Purchase #3 $161.43   7.445%   $173.4485   $173.45   $173.45   $173.40  
  Purchase #4 $119.65   11.873%   $133.856   $133.86   $133.85   $133.90  
  Purchase #5 $190.46   11.869%   $213.0657   $213.07   $213.05   $213.10  
  Purchase #6 $155.26   13.782%   $176.6579   $176.66   $176.65   $176.70  
  Purchase #7 $213.69   8.664%   $232.2041   $232.20   $232.20   $232.20  
  7 purchase totals = $1,009.97       $1,114.0699   $1,114.08   $1,114.00   $1,114.10