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 $176.98   10.384%   $195.3576   $195.36   $195.35   $195.40  
  Purchase #2 $230.75   3.142%   $238.0002   $238.00   $238.00   $238.00  
  Purchase #3 $226.67   10.479%   $250.4227   $250.42   $250.40   $250.40  
  Purchase #4 $146.63   10.841%   $162.5262   $162.53   $162.55   $162.50  
  Purchase #5 $245.39   6.781%   $262.0299   $262.03   $262.05   $262.00  
  Purchase #6 $52.55   8.442%   $56.9863   $56.99   $57.00   $57.00  
  Purchase #7 $219.93   12.104%   $246.5503   $246.55   $246.55   $246.60  
  7 purchase totals = $1,298.90       $1,411.8732   $1,411.88   $1,411.90   $1,411.90