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 $29.26   8.265%   $31.6783   $31.68   $31.70   $31.70  
  Purchase #2 $197.28   4.355%   $205.8715   $205.87   $205.85   $205.90  
  Purchase #3 $153.40   8.230%   $166.0248   $166.02   $166.00   $166.00  
  Purchase #4 $179.56   7.835%   $193.6285   $193.63   $193.65   $193.60  
  Purchase #5 $20.62   6.247%   $21.9081   $21.91   $21.90   $21.90  
  Purchase #6 $210.98   3.181%   $217.6913   $217.69   $217.70   $217.70  
  Purchase #7 $179.29   9.418%   $196.1755   $196.18   $196.20   $196.20  
  7 purchase totals = $970.39       $1,032.9780   $1,032.98   $1,033.00   $1,033.00