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 $34.47   9.362%   $37.6971   $37.70   $37.70   $37.70  
  Purchase #2 $248.31   10.810%   $275.1523   $275.15   $275.15   $275.20  
  Purchase #3 $161.43   9.235%   $176.3381   $176.34   $176.35   $176.30  
  Purchase #4 $156.54   6.407%   $166.5695   $166.57   $166.55   $166.60  
  Purchase #5 $197.95   3.711%   $205.2959   $205.30   $205.30   $205.30  
  Purchase #6 $162.32   6.396%   $172.702   $172.70   $172.70   $172.70  
  Purchase #7 $222.79   4.661%   $233.1742   $233.17   $233.15   $233.20  
  7 purchase totals = $1,183.81       $1,266.9291   $1,266.93   $1,266.90   $1,267.00