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 $84.51   9.773%   $92.7692   $92.77   $92.75   $92.80  
  Purchase #2 $61.68   6.708%   $65.8175   $65.82   $65.80   $65.80  
  Purchase #3 $96.84   13.501%   $109.9144   $109.91   $109.90   $109.90  
  Purchase #4 $242.81   7.756%   $261.6423   $261.64   $261.65   $261.60  
  Purchase #5 $225.60   10.104%   $248.3946   $248.39   $248.40   $248.40  
  Purchase #6 $200.77   4.657%   $210.1199   $210.12   $210.10   $210.10  
  Purchase #7 $212.28   4.323%   $221.4569   $221.46   $221.45   $221.50  
  7 purchase totals = $1,124.49       $1,210.1148   $1,210.11   $1,210.05   $1,210.10