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	$20.37	9.359%	$22.2764	$22.28	$22.30	$22.30
Purchase #2	$40.83	6.750%	$43.586	$43.59	$43.60	$43.60
Purchase #3	$65.83	11.689%	$73.5249	$73.52	$73.50	$73.50
Purchase #4	$84.34	4.790%	$88.3799	$88.38	$88.40	$88.40
Purchase #5	$111.69	11.635%	$124.6851	$124.69	$124.70	$124.70
Purchase #6	$99.86	7.271%	$107.1208	$107.12	$107.10	$107.10
Purchase #7	$105.45	12.780%	$118.9265	$118.93	$118.95	$118.90
7 purchase totals =	$528.37		$578.4996	$578.51	$578.55	$578.50