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 $173.60   11.822%   $194.123   $194.12   $194.10   $194.10  
  Purchase #2 $161.65   10.516%   $178.6491   $178.65   $178.65   $178.60  
  Purchase #3 $249.81   5.500%   $263.5496   $263.55   $263.55   $263.50  
  Purchase #4 $250.88   7.465%   $269.6082   $269.61   $269.60   $269.60  
  Purchase #5 $46.31   13.170%   $52.409   $52.41   $52.40   $52.40  
  Purchase #6 $147.37   3.493%   $152.5176   $152.52   $152.50   $152.50  
  Purchase #7 $88.97   6.135%   $94.4283   $94.43   $94.45   $94.40  
  7 purchase totals = $1,118.59       $1,205.2848   $1,205.29   $1,205.25   $1,205.10