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 $68.29   8.347%   $73.9902   $73.99   $74.00   $74.00  
  Purchase #2 $155.67   11.110%   $172.9649   $172.96   $172.95   $173.00  
  Purchase #3 $51.71   4.107%   $53.8337   $53.83   $53.85   $53.80  
  Purchase #4 $197.86   8.771%   $215.2143   $215.21   $215.20   $215.20  
  Purchase #5 $177.66   11.587%   $198.2455   $198.25   $198.25   $198.20  
  Purchase #6 $244.64   9.674%   $268.3065   $268.31   $268.30   $268.30  
  Purchase #7 $152.47   10.622%   $168.6654   $168.67   $168.65   $168.70  
  7 purchase totals = $1,048.30       $1,151.2205   $1,151.22   $1,151.20   $1,151.20