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 $182.44   5.549%   $192.5636   $192.56   $192.55   $192.60  
  Purchase #2 $67.69   8.181%   $73.2277   $73.23   $73.25   $73.20  
  Purchase #3 $60.40   10.373%   $66.6653   $66.67   $66.65   $66.70  
  Purchase #4 $34.84   9.781%   $38.2477   $38.25   $38.25   $38.20  
  Purchase #5 $93.64   3.133%   $96.5737   $96.57   $96.55   $96.60  
  Purchase #6 $187.87   8.728%   $204.2673   $204.27   $204.25   $204.30  
  Purchase #7 $200.32   5.257%   $210.8508   $210.85   $210.85   $210.90  
  7 purchase totals = $827.20       $882.3961   $882.40   $882.35   $882.50