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	$79.48	3.508%	$82.2682	$82.27	$82.25	$82.30
Purchase #2	$53.87	10.205%	$59.3674	$59.37	$59.35	$59.40
Purchase #3	$231.73	13.113%	$262.1168	$262.12	$262.10	$262.10
Purchase #4	$133.66	8.271%	$144.715	$144.72	$144.70	$144.70
Purchase #5	$224.65	9.514%	$246.0232	$246.02	$246.00	$246.00
Purchase #6	$110.51	3.872%	$114.7889	$114.79	$114.80	$114.80
Purchase #7	$146.40	6.604%	$156.0683	$156.07	$156.05	$156.10
7 purchase totals =	$980.30		$1,065.3478	$1,065.36	$1,065.25	$1,065.40