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 $182.71   6.734%   $195.0137   $195.01   $195.00   $195.00  
  Purchase #2 $168.26   3.108%   $173.4895   $173.49   $173.50   $173.50  
  Purchase #3 $201.69   7.209%   $216.2298   $216.23   $216.25   $216.20  
  Purchase #4 $186.75   3.713%   $193.684   $193.68   $193.70   $193.70  
  Purchase #5 $111.60   6.203%   $118.5225   $118.52   $118.50   $118.50  
  Purchase #6 $142.26   11.345%   $158.3994   $158.40   $158.40   $158.40  
  Purchase #7 $244.88   6.380%   $260.5033   $260.50   $260.50   $260.50  
  7 purchase totals = $1,238.15       $1,315.8422   $1,315.83   $1,315.85   $1,315.80