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 $221.57   5.136%   $232.9498   $232.95   $232.95   $232.90  
  Purchase #2 $52.32   8.140%   $56.5788   $56.58   $56.60   $56.60  
  Purchase #3 $186.80   10.427%   $206.2776   $206.28   $206.30   $206.30  
  Purchase #4 $51.75   3.267%   $53.4407   $53.44   $53.45   $53.40  
  Purchase #5 $124.25   5.229%   $130.747   $130.75   $130.75   $130.70  
  Purchase #6 $193.26   5.651%   $204.1811   $204.18   $204.20   $204.20  
  Purchase #7 $169.72   13.251%   $192.2096   $192.21   $192.20   $192.20  
  7 purchase totals = $999.67       $1,076.3846   $1,076.39   $1,076.45   $1,076.30