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 $166.50   5.850%   $176.2403   $176.24   $176.25   $176.20  
  Purchase #2 $197.59   3.534%   $204.5728   $204.57   $204.55   $204.60  
  Purchase #3 $64.44   8.647%   $70.0121   $70.01   $70.00   $70.00  
  Purchase #4 $135.87   8.635%   $147.6024   $147.60   $147.60   $147.60  
  Purchase #5 $134.72   7.454%   $144.762   $144.76   $144.75   $144.80  
  Purchase #6 $235.91   13.442%   $267.621   $267.62   $267.60   $267.60  
  Purchase #7 $171.48   6.302%   $182.2867   $182.29   $182.30   $182.30  
  7 purchase totals = $1,106.51       $1,193.0973   $1,193.09   $1,193.05   $1,193.10