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 $184.96   5.426%   $194.9959   $195.00   $195.00   $195.00  
  Purchase #2 $60.37   11.766%   $67.4731   $67.47   $67.45   $67.50  
  Purchase #3 $41.66   12.292%   $46.7808   $46.78   $46.80   $46.80  
  Purchase #4 $86.62   9.663%   $94.9901   $94.99   $95.00   $95.00  
  Purchase #5 $94.32   3.652%   $97.7646   $97.76   $97.75   $97.80  
  Purchase #6 $250.45   13.470%   $284.1856   $284.19   $284.20   $284.20  
  Purchase #7 $249.53   4.237%   $260.1026   $260.10   $260.10   $260.10  
  7 purchase totals = $967.91       $1,046.2927   $1,046.29   $1,046.30   $1,046.40