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	$39.29	9.443%	$43.0002	$43.00	$43.00	$43.00
Purchase #2	$171.27	12.486%	$192.6548	$192.65	$192.65	$192.70
Purchase #3	$57.66	10.167%	$63.5223	$63.52	$63.50	$63.50
Purchase #4	$133.33	6.844%	$142.4551	$142.46	$142.45	$142.50
Purchase #5	$40.63	4.871%	$42.6091	$42.61	$42.60	$42.60
Purchase #6	$19.60	13.380%	$22.2225	$22.22	$22.20	$22.20
Purchase #7	$219.29	5.751%	$231.9014	$231.90	$231.90	$231.90
7 purchase totals =	$681.07		$738.3654	$738.36	$738.30	$738.40