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 $95.51   5.604%   $100.8624   $100.86   $100.85   $100.90  
  Purchase #2 $194.89   3.627%   $201.9587   $201.96   $201.95   $202.00  
  Purchase #3 $235.65   7.528%   $253.3897   $253.39   $253.40   $253.40  
  Purchase #4 $153.56   6.569%   $163.6474   $163.65   $163.65   $163.60  
  Purchase #5 $148.33   13.643%   $168.5667   $168.57   $168.55   $168.60  
  Purchase #6 $221.68   6.865%   $236.8983   $236.90   $236.90   $236.90  
  Purchase #7 $55.51   5.773%   $58.7146   $58.71   $58.70   $58.70  
  7 purchase totals = $1,105.13       $1,184.0378   $1,184.04   $1,184.00   $1,184.10