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 $85.43   12.309%   $95.9456   $95.95   $95.95   $95.90  
  Purchase #2 $174.91   9.874%   $192.1806   $192.18   $192.20   $192.20  
  Purchase #3 $80.80   9.212%   $88.2433   $88.24   $88.25   $88.20  
  Purchase #4 $205.41   13.204%   $232.5323   $232.53   $232.55   $232.50  
  Purchase #5 $84.55   13.330%   $95.8205   $95.82   $95.80   $95.80  
  Purchase #6 $214.55   11.493%   $239.2082   $239.21   $239.20   $239.20  
  Purchase #7 $203.79   11.348%   $226.9161   $226.92   $226.90   $226.90  
  7 purchase totals = $1,049.44       $1,170.8466   $1,170.85   $1,170.85   $1,170.70