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 $88.70   6.334%   $94.3183   $94.32   $94.30   $94.30  
  Purchase #2 $131.50   12.280%   $147.6482   $147.65   $147.65   $147.60  
  Purchase #3 $205.63   6.226%   $218.4325   $218.43   $218.45   $218.40  
  Purchase #4 $130.57   6.271%   $138.758   $138.76   $138.75   $138.80  
  Purchase #5 $133.89   9.364%   $146.4275   $146.43   $146.45   $146.40  
  Purchase #6 $138.60   6.824%   $148.0581   $148.06   $148.05   $148.10  
  Purchase #7 $152.62   10.583%   $168.7718   $168.77   $168.75   $168.80  
  7 purchase totals = $981.51       $1,062.4144   $1,062.42   $1,062.40   $1,062.40