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 $168.33   4.561%   $176.0075   $176.01   $176.00   $176.00  
  Purchase #2 $230.96   7.314%   $247.8524   $247.85   $247.85   $247.90  
  Purchase #3 $16.83   3.843%   $17.4768   $17.48   $17.50   $17.50  
  Purchase #4 $115.88   6.234%   $123.104   $123.10   $123.10   $123.10  
  Purchase #5 $75.46   11.565%   $84.1869   $84.19   $84.20   $84.20  
  Purchase #6 $233.52   3.830%   $242.4638   $242.46   $242.45   $242.50  
  Purchase #7 $195.30   10.602%   $216.0057   $216.01   $216.00   $216.00  
  7 purchase totals = $1,036.28       $1,107.0971   $1,107.10   $1,107.10   $1,107.20