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 $94.99   5.485%   $100.2002   $100.20   $100.20   $100.20  
  Purchase #2 $153.91   8.635%   $167.2001   $167.20   $167.20   $167.20  
  Purchase #3 $202.96   10.627%   $224.5286   $224.53   $224.55   $224.50  
  Purchase #4 $230.41   12.647%   $259.55   $259.55   $259.55   $259.60  
  Purchase #5 $134.59   13.400%   $152.6251   $152.63   $152.65   $152.60  
  Purchase #6 $118.37   3.437%   $122.4384   $122.44   $122.45   $122.40  
  Purchase #7 $180.72   10.331%   $199.3902   $199.39   $199.40   $199.40  
  7 purchase totals = $1,115.95       $1,225.9326   $1,225.94   $1,226.00   $1,225.90