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	$69.97	4.712%	$73.267	$73.27	$73.25	$73.30
Purchase #2	$23.28	11.351%	$25.9225	$25.92	$25.90	$25.90
Purchase #3	$227.72	5.414%	$240.0488	$240.05	$240.05	$240.00
Purchase #4	$238.42	3.479%	$246.7146	$246.71	$246.70	$246.70
Purchase #5	$159.34	12.256%	$178.8687	$178.87	$178.85	$178.90
Purchase #6	$16.27	10.680%	$18.0076	$18.01	$18.00	$18.00
Purchase #7	$219.90	6.117%	$233.3513	$233.35	$233.35	$233.40
7 purchase totals =	$954.90		$1,016.1805	$1,016.18	$1,016.10	$1,016.20