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 $89.29   7.362%   $95.8635   $95.86   $95.85   $95.90  
  Purchase #2 $106.55   3.266%   $110.0299   $110.03   $110.05   $110.00  
  Purchase #3 $91.38   5.485%   $96.3922   $96.39   $96.40   $96.40  
  Purchase #4 $114.55   9.440%   $125.3635   $125.36   $125.35   $125.40  
  Purchase #5 $65.88   3.478%   $68.1713   $68.17   $68.15   $68.20  
  Purchase #6 $239.41   9.531%   $262.2282   $262.23   $262.25   $262.20  
  Purchase #7 $174.28   8.157%   $188.496   $188.50   $188.50   $188.50  
  7 purchase totals = $881.34       $946.5446   $946.54   $946.55   $946.60