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 $160.33   13.765%   $182.3994   $182.40   $182.40   $182.40  
  Purchase #2 $55.90   8.341%   $60.5626   $60.56   $60.55   $60.60  
  Purchase #3 $10.65   6.608%   $11.3538   $11.35   $11.35   $11.40  
  Purchase #4 $205.59   13.359%   $233.0548   $233.05   $233.05   $233.10  
  Purchase #5 $126.79   12.215%   $142.2774   $142.28   $142.30   $142.30  
  Purchase #6 $203.37   3.313%   $210.1076   $210.11   $210.10   $210.10  
  Purchase #7 $249.69   9.736%   $273.9998   $274.00   $274.00   $274.00  
  7 purchase totals = $1,012.32       $1,113.7554   $1,113.75   $1,113.75   $1,113.90