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 $184.90   7.251%   $198.3071   $198.31   $198.30   $198.30  
  Purchase #2 $149.33   5.167%   $157.0459   $157.05   $157.05   $157.00  
  Purchase #3 $115.93   10.226%   $127.785   $127.79   $127.80   $127.80  
  Purchase #4 $58.49   6.310%   $62.1807   $62.18   $62.20   $62.20  
  Purchase #5 $240.26   3.579%   $248.8589   $248.86   $248.85   $248.90  
  Purchase #6 $214.59   10.248%   $236.5812   $236.58   $236.60   $236.60  
  Purchase #7 $212.47   9.223%   $232.0661   $232.07   $232.05   $232.10  
  7 purchase totals = $1,175.97       $1,262.8249   $1,262.84   $1,262.85   $1,262.90