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 $167.51   5.284%   $176.3612   $176.36   $176.35   $176.40  
  Purchase #2 $205.35   12.124%   $230.2466   $230.25   $230.25   $230.20  
  Purchase #3 $165.47   3.728%   $171.6387   $171.64   $171.65   $171.60  
  Purchase #4 $82.94   13.367%   $94.0266   $94.03   $94.05   $94.00  
  Purchase #5 $187.92   11.143%   $208.8599   $208.86   $208.85   $208.90  
  Purchase #6 $226.92   3.656%   $235.2162   $235.22   $235.20   $235.20  
  Purchase #7 $87.46   7.627%   $94.1306   $94.13   $94.15   $94.10  
  7 purchase totals = $1,123.57       $1,210.4798   $1,210.49   $1,210.50   $1,210.40