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 $65.86   11.148%   $73.2021   $73.20   $73.20   $73.20  
  Purchase #2 $249.31   7.117%   $267.0534   $267.05   $267.05   $267.10  
  Purchase #3 $186.55   5.867%   $197.4949   $197.49   $197.50   $197.50  
  Purchase #4 $160.75   4.792%   $168.4531   $168.45   $168.45   $168.50  
  Purchase #5 $240.95   9.432%   $263.6764   $263.68   $263.70   $263.70  
  Purchase #6 $244.41   9.261%   $267.0448   $267.04   $267.05   $267.00  
  Purchase #7 $157.86   10.383%   $174.2506   $174.25   $174.25   $174.30  
  7 purchase totals = $1,305.69       $1,411.1753   $1,411.16   $1,411.20   $1,411.30