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 $215.51   9.349%   $235.658   $235.66   $235.65   $235.70  
  Purchase #2 $108.64   9.580%   $119.0477   $119.05   $119.05   $119.00  
  Purchase #3 $41.34   5.552%   $43.6352   $43.64   $43.65   $43.60  
  Purchase #4 $95.97   10.309%   $105.8635   $105.86   $105.85   $105.90  
  Purchase #5 $8.80   6.387%   $9.3621   $9.36   $9.35   $9.40  
  Purchase #6 $163.33   6.204%   $173.463   $173.46   $173.45   $173.50  
  Purchase #7 $31.77   11.464%   $35.4121   $35.41   $35.40   $35.40  
  7 purchase totals = $665.36       $722.4416   $722.44   $722.40   $722.50