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 $108.26   5.103%   $113.7845   $113.78   $113.80   $113.80  
  Purchase #2 $100.78   8.247%   $109.0913   $109.09   $109.10   $109.10  
  Purchase #3 $49.34   8.433%   $53.5008   $53.50   $53.50   $53.50  
  Purchase #4 $216.65   6.203%   $230.0888   $230.09   $230.10   $230.10  
  Purchase #5 $44.95   3.547%   $46.5444   $46.54   $46.55   $46.50  
  Purchase #6 $193.42   10.314%   $213.3693   $213.37   $213.35   $213.40  
  Purchase #7 $160.28   8.726%   $174.266   $174.27   $174.25   $174.30  
  7 purchase totals = $873.68       $940.6451   $940.64   $940.65   $940.70