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 $206.75   7.839%   $222.9571   $222.96   $222.95   $223.00  
  Purchase #2 $99.69   13.352%   $113.0006   $113.00   $113.00   $113.00  
  Purchase #3 $153.37   6.799%   $163.7976   $163.80   $163.80   $163.80  
  Purchase #4 $203.64   8.494%   $220.9372   $220.94   $220.95   $220.90  
  Purchase #5 $218.47   10.590%   $241.606   $241.61   $241.60   $241.60  
  Purchase #6 $245.67   6.718%   $262.1741   $262.17   $262.15   $262.20  
  Purchase #7 $197.52   6.676%   $210.7064   $210.71   $210.70   $210.70  
  7 purchase totals = $1,325.11       $1,435.1790   $1,435.19   $1,435.15   $1,435.20