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 $49.36   9.319%   $53.9599   $53.96   $53.95   $54.00  
  Purchase #2 $178.77   8.654%   $194.2408   $194.24   $194.25   $194.20  
  Purchase #3 $217.49   8.432%   $235.8288   $235.83   $235.85   $235.80  
  Purchase #4 $231.54   9.547%   $253.6451   $253.65   $253.65   $253.60  
  Purchase #5 $37.43   13.283%   $42.4018   $42.40   $42.40   $42.40  
  Purchase #6 $158.45   12.614%   $178.4369   $178.44   $178.45   $178.40  
  Purchase #7 $89.71   8.231%   $97.094   $97.09   $97.10   $97.10  
  7 purchase totals = $962.75       $1,055.6073   $1,055.61   $1,055.65   $1,055.50