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 $148.67   9.187%   $162.3283   $162.33   $162.35   $162.30  
  Purchase #2 $213.70   6.369%   $227.3106   $227.31   $227.30   $227.30  
  Purchase #3 $186.80   6.744%   $199.3978   $199.40   $199.40   $199.40  
  Purchase #4 $10.62   9.524%   $11.6314   $11.63   $11.65   $11.60  
  Purchase #5 $48.50   9.282%   $53.0018   $53.00   $53.00   $53.00  
  Purchase #6 $220.93   13.585%   $250.9433   $250.94   $250.95   $250.90  
  Purchase #7 $46.67   5.706%   $49.333   $49.33   $49.35   $49.30  
  7 purchase totals = $875.89       $953.9462   $953.94   $954.00   $953.80