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 $88.50   10.765%   $98.027   $98.03   $98.05   $98.00  
  Purchase #2 $132.65   11.551%   $147.9724   $147.97   $147.95   $148.00  
  Purchase #3 $107.47   7.594%   $115.6313   $115.63   $115.65   $115.60  
  Purchase #4 $202.37   10.263%   $223.1392   $223.14   $223.15   $223.10  
  Purchase #5 $79.25   10.566%   $87.6236   $87.62   $87.60   $87.60  
  Purchase #6 $85.41   8.251%   $92.4572   $92.46   $92.45   $92.50  
  Purchase #7 $180.60   3.418%   $186.7729   $186.77   $186.75   $186.80  
  7 purchase totals = $876.25       $951.6236   $951.62   $951.60   $951.60