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 $60.26   8.403%   $65.3236   $65.32   $65.30   $65.30  
  Purchase #2 $173.67   13.145%   $196.4989   $196.50   $196.50   $196.50  
  Purchase #3 $7.60   8.791%   $8.2681   $8.27   $8.25   $8.30  
  Purchase #4 $219.36   10.605%   $242.6231   $242.62   $242.60   $242.60  
  Purchase #5 $217.69   7.741%   $234.5414   $234.54   $234.55   $234.50  
  Purchase #6 $234.84   10.103%   $258.5659   $258.57   $258.55   $258.60  
  Purchase #7 $109.57   8.790%   $119.2012   $119.20   $119.20   $119.20  
  7 purchase totals = $1,022.99       $1,125.0222   $1,125.02   $1,124.95   $1,125.00