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 $202.66   5.695%   $214.2015   $214.20   $214.20   $214.20  
  Purchase #2 $122.68   7.733%   $132.1668   $132.17   $132.15   $132.20  
  Purchase #3 $166.51   9.564%   $182.435   $182.44   $182.45   $182.40  
  Purchase #4 $73.47   6.304%   $78.1015   $78.10   $78.10   $78.10  
  Purchase #5 $45.76   11.229%   $50.8984   $50.90   $50.90   $50.90  
  Purchase #6 $57.50   8.395%   $62.3271   $62.33   $62.35   $62.30  
  Purchase #7 $23.93   9.214%   $26.1349   $26.13   $26.15   $26.10  
  7 purchase totals = $692.51       $746.2652   $746.27   $746.30   $746.20