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 $54.93   7.301%   $58.9404   $58.94   $58.95   $58.90  
  Purchase #2 $248.37   4.201%   $258.804   $258.80   $258.80   $258.80  
  Purchase #3 $94.53   9.612%   $103.6162   $103.62   $103.60   $103.60  
  Purchase #4 $163.52   8.864%   $178.0144   $178.01   $178.00   $178.00  
  Purchase #5 $237.48   5.115%   $249.6271   $249.63   $249.65   $249.60  
  Purchase #6 $148.62   3.722%   $154.1516   $154.15   $154.15   $154.20  
  Purchase #7 $96.54   10.855%   $107.0194   $107.02   $107.00   $107.00  
  7 purchase totals = $1,043.99       $1,110.1731   $1,110.17   $1,110.15   $1,110.10