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 $162.80   8.129%   $176.034   $176.03   $176.05   $176.00  
  Purchase #2 $66.41   12.328%   $74.597   $74.60   $74.60   $74.60  
  Purchase #3 $91.88   10.737%   $101.7452   $101.75   $101.75   $101.70  
  Purchase #4 $23.44   5.867%   $24.8152   $24.82   $24.80   $24.80  
  Purchase #5 $58.28   12.815%   $65.7486   $65.75   $65.75   $65.70  
  Purchase #6 $174.90   3.241%   $180.5685   $180.57   $180.55   $180.60  
  Purchase #7 $138.27   9.521%   $151.4347   $151.43   $151.45   $151.40  
  7 purchase totals = $715.98       $774.9432   $774.95   $774.95   $774.80