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 $42.36   10.623%   $46.8599   $46.86   $46.85   $46.90  
  Purchase #2 $109.97   7.507%   $118.2254   $118.23   $118.25   $118.20  
  Purchase #3 $29.39   8.165%   $31.7897   $31.79   $31.80   $31.80  
  Purchase #4 $114.89   3.257%   $118.632   $118.63   $118.65   $118.60  
  Purchase #5 $202.61   11.824%   $226.5666   $226.57   $226.55   $226.60  
  Purchase #6 $245.81   9.627%   $269.4741   $269.47   $269.45   $269.50  
  Purchase #7 $222.25   8.462%   $241.0568   $241.06   $241.05   $241.10  
  7 purchase totals = $967.28       $1,052.6045   $1,052.61   $1,052.60   $1,052.70