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	$189.81	13.208%	$214.8801	$214.88	$214.90	$214.90
Purchase #2	$160.92	11.491%	$179.4113	$179.41	$179.40	$179.40
Purchase #3	$52.59	9.787%	$57.737	$57.74	$57.75	$57.70
Purchase #4	$78.62	8.727%	$85.4812	$85.48	$85.50	$85.50
Purchase #5	$184.30	6.696%	$196.6407	$196.64	$196.65	$196.60
Purchase #6	$10.26	12.426%	$11.5349	$11.53	$11.55	$11.50
Purchase #7	$100.87	6.450%	$107.3761	$107.38	$107.40	$107.40
7 purchase totals =	$777.37		$853.0613	$853.06	$853.15	$853.00