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 $46.79   13.635%   $53.1698   $53.17   $53.15   $53.20  
  Purchase #2 $125.88   9.466%   $137.7958   $137.80   $137.80   $137.80  
  Purchase #3 $18.32   10.776%   $20.2942   $20.29   $20.30   $20.30  
  Purchase #4 $197.42   5.346%   $207.9741   $207.97   $207.95   $208.00  
  Purchase #5 $227.37   8.268%   $246.169   $246.17   $246.15   $246.20  
  Purchase #6 $232.64   4.871%   $243.9719   $243.97   $243.95   $244.00  
  Purchase #7 $182.86   12.273%   $205.3024   $205.30   $205.30   $205.30  
  7 purchase totals = $1,031.28       $1,114.6772   $1,114.67   $1,114.60   $1,114.80