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 $58.80   5.509%   $62.0393   $62.04   $62.05   $62.00  
  Purchase #2 $46.41   3.711%   $48.1323   $48.13   $48.15   $48.10  
  Purchase #3 $153.65   13.690%   $174.6847   $174.68   $174.70   $174.70  
  Purchase #4 $45.50   8.207%   $49.2342   $49.23   $49.25   $49.20  
  Purchase #5 $25.69   11.303%   $28.5937   $28.59   $28.60   $28.60  
  Purchase #6 $222.56   5.177%   $234.0819   $234.08   $234.10   $234.10  
  Purchase #7 $132.33   4.464%   $138.2372   $138.24   $138.25   $138.20  
  7 purchase totals = $684.94       $735.0033   $734.99   $735.10   $734.90