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 $177.27   11.446%   $197.5603   $197.56   $197.55   $197.60  
  Purchase #2 $164.29   6.298%   $174.637   $174.64   $174.65   $174.60  
  Purchase #3 $161.60   4.313%   $168.5698   $168.57   $168.55   $168.60  
  Purchase #4 $49.40   3.740%   $51.2476   $51.25   $51.25   $51.20  
  Purchase #5 $72.83   3.138%   $75.1154   $75.12   $75.10   $75.10  
  Purchase #6 $222.55   8.855%   $242.2568   $242.26   $242.25   $242.30  
  Purchase #7 $244.33   5.791%   $258.4792   $258.48   $258.50   $258.50  
  7 purchase totals = $1,092.27       $1,167.8661   $1,167.88   $1,167.85   $1,167.90