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 $44.75   7.828%   $48.253   $48.25   $48.25   $48.30  
  Purchase #2 $112.32   11.275%   $124.9841   $124.98   $125.00   $125.00  
  Purchase #3 $155.53   13.551%   $176.6059   $176.61   $176.60   $176.60  
  Purchase #4 $48.75   7.118%   $52.22   $52.22   $52.20   $52.20  
  Purchase #5 $181.47   5.679%   $191.7757   $191.78   $191.80   $191.80  
  Purchase #6 $71.36   8.806%   $77.644   $77.64   $77.65   $77.60  
  Purchase #7 $176.82   5.501%   $186.5469   $186.55   $186.55   $186.50  
  7 purchase totals = $791.00       $858.0296   $858.03   $858.05   $858.00