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 $86.98   6.505%   $92.638   $92.64   $92.65   $92.60  
  Purchase #2 $161.48   11.209%   $179.5803   $179.58   $179.60   $179.60  
  Purchase #3 $180.80   6.568%   $192.6749   $192.67   $192.65   $192.70  
  Purchase #4 $211.34   5.245%   $222.4248   $222.42   $222.40   $222.40  
  Purchase #5 $161.42   6.537%   $171.972   $171.97   $171.95   $172.00  
  Purchase #6 $134.78   4.124%   $140.3383   $140.34   $140.35   $140.30  
  Purchase #7 $199.58   13.554%   $226.6311   $226.63   $226.65   $226.60  
  7 purchase totals = $1,136.38       $1,226.2594   $1,226.25   $1,226.25   $1,226.20