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 $172.48   5.609%   $182.1544   $182.15   $182.15   $182.20  
  Purchase #2 $187.46   4.519%   $195.9313   $195.93   $195.95   $195.90  
  Purchase #3 $38.80   11.404%   $43.2248   $43.22   $43.20   $43.20  
  Purchase #4 $44.63   5.362%   $47.0231   $47.02   $47.00   $47.00  
  Purchase #5 $165.99   4.673%   $173.7467   $173.75   $173.75   $173.70  
  Purchase #6 $234.67   13.793%   $267.038   $267.04   $267.05   $267.00  
  Purchase #7 $141.29   13.670%   $160.6043   $160.60   $160.60   $160.60  
  7 purchase totals = $985.32       $1,069.7226   $1,069.71   $1,069.70   $1,069.60