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 $88.39   7.838%   $95.318   $95.32   $95.30   $95.30  
  Purchase #2 $128.51   7.363%   $137.9722   $137.97   $137.95   $138.00  
  Purchase #3 $208.55   9.202%   $227.7408   $227.74   $227.75   $227.70  
  Purchase #4 $164.87   4.194%   $171.7846   $171.78   $171.80   $171.80  
  Purchase #5 $142.48   13.111%   $161.1606   $161.16   $161.15   $161.20  
  Purchase #6 $112.90   9.509%   $123.6357   $123.64   $123.65   $123.60  
  Purchase #7 $94.66   13.199%   $107.1542   $107.15   $107.15   $107.20  
  7 purchase totals = $940.36       $1,024.7661   $1,024.76   $1,024.75   $1,024.80