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 $197.97   10.716%   $219.1845   $219.18   $219.20   $219.20  
  Purchase #2 $171.65   11.405%   $191.2267   $191.23   $191.25   $191.20  
  Purchase #3 $183.44   9.274%   $200.4522   $200.45   $200.45   $200.50  
  Purchase #4 $57.94   4.852%   $60.7512   $60.75   $60.75   $60.80  
  Purchase #5 $245.34   4.855%   $257.2513   $257.25   $257.25   $257.30  
  Purchase #6 $198.46   3.616%   $205.6363   $205.64   $205.65   $205.60  
  Purchase #7 $202.80   4.412%   $211.7475   $211.75   $211.75   $211.70  
  7 purchase totals = $1,257.60       $1,346.2497   $1,346.25   $1,346.30   $1,346.30