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 $64.83   12.635%   $73.0213   $73.02   $73.00   $73.00  
  Purchase #2 $212.84   11.388%   $237.0782   $237.08   $237.10   $237.10  
  Purchase #3 $41.33   7.133%   $44.2781   $44.28   $44.30   $44.30  
  Purchase #4 $104.26   6.130%   $110.6511   $110.65   $110.65   $110.70  
  Purchase #5 $122.94   12.150%   $137.8772   $137.88   $137.90   $137.90  
  Purchase #6 $5.33   9.566%   $5.8399   $5.84   $5.85   $5.80  
  Purchase #7 $102.75   11.187%   $114.2446   $114.24   $114.25   $114.20  
  7 purchase totals = $654.28       $722.9904   $722.99   $723.05   $723.00