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 $233.80   11.503%   $260.694   $260.69   $260.70   $260.70  
  Purchase #2 $244.57   6.446%   $260.335   $260.34   $260.35   $260.30  
  Purchase #3 $27.56   6.431%   $29.3324   $29.33   $29.35   $29.30  
  Purchase #4 $104.97   4.611%   $109.8102   $109.81   $109.80   $109.80  
  Purchase #5 $164.68   6.795%   $175.87   $175.87   $175.85   $175.90  
  Purchase #6 $118.58   12.394%   $133.2768   $133.28   $133.30   $133.30  
  Purchase #7 $192.60   6.591%   $205.2943   $205.29   $205.30   $205.30  
  7 purchase totals = $1,086.76       $1,174.6127   $1,174.61   $1,174.65   $1,174.60