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 $84.26   9.244%   $92.049   $92.05   $92.05   $92.00  
  Purchase #2 $76.82   13.190%   $86.9526   $86.95   $86.95   $87.00  
  Purchase #3 $161.42   13.569%   $183.3231   $183.32   $183.30   $183.30  
  Purchase #4 $226.98   3.799%   $235.603   $235.60   $235.60   $235.60  
  Purchase #5 $226.90   10.566%   $250.8743   $250.87   $250.85   $250.90  
  Purchase #6 $12.32   10.800%   $13.6506   $13.65   $13.65   $13.70  
  Purchase #7 $168.65   6.211%   $179.1249   $179.12   $179.10   $179.10  
  7 purchase totals = $957.35       $1,041.5775   $1,041.56   $1,041.50   $1,041.60