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 $87.94   8.717%   $95.6057   $95.61   $95.60   $95.60  
  Purchase #2 $233.65   6.172%   $248.0709   $248.07   $248.05   $248.10  
  Purchase #3 $222.94   8.429%   $241.7316   $241.73   $241.75   $241.70  
  Purchase #4 $205.63   7.395%   $220.8363   $220.84   $220.85   $220.80  
  Purchase #5 $106.33   10.531%   $117.5276   $117.53   $117.55   $117.50  
  Purchase #6 $127.88   13.358%   $144.9622   $144.96   $144.95   $145.00  
  Purchase #7 $239.99   5.690%   $253.6454   $253.65   $253.65   $253.60  
  7 purchase totals = $1,224.36       $1,322.3797   $1,322.39   $1,322.40   $1,322.30