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 $49.76   8.232%   $53.8562   $53.86   $53.85   $53.90  
  Purchase #2 $134.96   12.214%   $151.444   $151.44   $151.45   $151.40  
  Purchase #3 $95.64   11.323%   $106.4693   $106.47   $106.45   $106.50  
  Purchase #4 $192.85   4.871%   $202.2437   $202.24   $202.25   $202.20  
  Purchase #5 $224.86   7.167%   $240.9757   $240.98   $241.00   $241.00  
  Purchase #6 $182.46   9.506%   $199.8046   $199.80   $199.80   $199.80  
  Purchase #7 $101.44   12.717%   $114.3401   $114.34   $114.35   $114.30  
  7 purchase totals = $981.97       $1,069.1336   $1,069.13   $1,069.15   $1,069.10