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 $72.25   3.427%   $74.726   $74.73   $74.75   $74.70  
  Purchase #2 $233.69   7.178%   $250.4643   $250.46   $250.45   $250.50  
  Purchase #3 $165.77   5.447%   $174.7995   $174.80   $174.80   $174.80  
  Purchase #4 $158.48   11.637%   $176.9223   $176.92   $176.90   $176.90  
  Purchase #5 $125.35   13.788%   $142.6333   $142.63   $142.65   $142.60  
  Purchase #6 $175.63   10.503%   $194.0764   $194.08   $194.10   $194.10  
  Purchase #7 $185.86   3.452%   $192.2759   $192.28   $192.30   $192.30  
  7 purchase totals = $1,117.03       $1,205.8977   $1,205.90   $1,205.95   $1,205.90