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 $95.61   10.873%   $106.0057   $106.01   $106.00   $106.00  
  Purchase #2 $212.35   9.253%   $231.9987   $232.00   $232.00   $232.00  
  Purchase #3 $25.83   5.470%   $27.2429   $27.24   $27.25   $27.20  
  Purchase #4 $54.82   5.721%   $57.9563   $57.96   $57.95   $58.00  
  Purchase #5 $53.65   13.659%   $60.9781   $60.98   $61.00   $61.00  
  Purchase #6 $198.47   6.121%   $210.6183   $210.62   $210.60   $210.60  
  Purchase #7 $71.45   13.399%   $81.0236   $81.02   $81.00   $81.00  
  7 purchase totals = $712.18       $775.8236   $775.83   $775.80   $775.80