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	$178.43	9.533%	$195.4397	$195.44	$195.45	$195.40
Purchase #2	$71.32	12.839%	$80.4768	$80.48	$80.50	$80.50
Purchase #3	$109.81	3.382%	$113.5238	$113.52	$113.50	$113.50
Purchase #4	$40.58	7.354%	$43.5643	$43.56	$43.55	$43.60
Purchase #5	$54.39	12.415%	$61.1425	$61.14	$61.15	$61.10
Purchase #6	$201.27	12.323%	$226.0725	$226.07	$226.05	$226.10
Purchase #7	$159.61	9.808%	$175.2645	$175.26	$175.25	$175.30
7 purchase totals =	$815.41		$895.4841	$895.47	$895.45	$895.50