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 $176.75   5.391%   $186.2786   $186.28   $186.30   $186.30  
  Purchase #2 $11.84   3.773%   $12.2867   $12.29   $12.30   $12.30  
  Purchase #3 $51.67   3.650%   $53.556   $53.56   $53.55   $53.60  
  Purchase #4 $233.97   6.469%   $249.1055   $249.11   $249.10   $249.10  
  Purchase #5 $247.57   8.237%   $267.9623   $267.96   $267.95   $268.00  
  Purchase #6 $190.77   8.592%   $207.161   $207.16   $207.15   $207.20  
  Purchase #7 $221.79   5.262%   $233.4606   $233.46   $233.45   $233.50  
  7 purchase totals = $1,134.36       $1,209.8107   $1,209.82   $1,209.80   $1,210.00