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 $195.48   9.483%   $214.0174   $214.02   $214.00   $214.00  
  Purchase #2 $118.99   6.230%   $126.4031   $126.40   $126.40   $126.40  
  Purchase #3 $156.49   3.710%   $162.2958   $162.30   $162.30   $162.30  
  Purchase #4 $81.39   7.630%   $87.6001   $87.60   $87.60   $87.60  
  Purchase #5 $181.82   5.401%   $191.6401   $191.64   $191.65   $191.60  
  Purchase #6 $94.49   3.184%   $97.4986   $97.50   $97.50   $97.50  
  Purchase #7 $65.38   7.334%   $70.175   $70.18   $70.20   $70.20  
  7 purchase totals = $894.04       $949.6301   $949.64   $949.65   $949.60