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 $164.68   7.449%   $176.947   $176.95   $176.95   $176.90  
  Purchase #2 $77.27   6.612%   $82.3791   $82.38   $82.40   $82.40  
  Purchase #3 $221.34   9.666%   $242.7347   $242.73   $242.75   $242.70  
  Purchase #4 $250.97   9.261%   $274.2123   $274.21   $274.20   $274.20  
  Purchase #5 $64.29   13.302%   $72.8419   $72.84   $72.85   $72.80  
  Purchase #6 $68.73   3.153%   $70.8971   $70.90   $70.90   $70.90  
  Purchase #7 $130.91   9.391%   $143.2038   $143.20   $143.20   $143.20  
  7 purchase totals = $978.19       $1,063.2159   $1,063.21   $1,063.25   $1,063.10