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	$197.59	11.760%	$220.8266	$220.83	$220.85	$220.80
Purchase #2	$39.43	3.553%	$40.8309	$40.83	$40.85	$40.80
Purchase #3	$179.35	3.548%	$185.7133	$185.71	$185.70	$185.70
Purchase #4	$136.31	3.451%	$141.0141	$141.01	$141.00	$141.00
Purchase #5	$76.44	4.346%	$79.7621	$79.76	$79.75	$79.80
Purchase #6	$50.66	6.365%	$53.8845	$53.88	$53.90	$53.90
Purchase #7	$126.74	4.870%	$132.9122	$132.91	$132.90	$132.90
7 purchase totals =	$806.52		$854.9437	$854.93	$854.95	$854.90