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 $118.75   5.466%   $125.2409   $125.24   $125.25   $125.20  
  Purchase #2 $149.49   8.249%   $161.8214   $161.82   $161.80   $161.80  
  Purchase #3 $73.42   8.155%   $79.4074   $79.41   $79.40   $79.40  
  Purchase #4 $143.65   12.835%   $162.0875   $162.09   $162.10   $162.10  
  Purchase #5 $233.29   6.267%   $247.9103   $247.91   $247.90   $247.90  
  Purchase #6 $94.97   8.353%   $102.9028   $102.90   $102.90   $102.90  
  Purchase #7 $119.75   13.251%   $135.6181   $135.62   $135.60   $135.60  
  7 purchase totals = $933.32       $1,014.9884   $1,014.99   $1,014.95   $1,014.90