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	$167.39	6.769%	$178.7206	$178.72	$178.70	$178.70
Purchase #2	$108.71	6.495%	$115.7707	$115.77	$115.75	$115.80
Purchase #3	$120.67	4.862%	$126.537	$126.54	$126.55	$126.50
Purchase #4	$107.34	3.720%	$111.333	$111.33	$111.35	$111.30
Purchase #5	$175.38	6.447%	$186.6867	$186.69	$186.70	$186.70
Purchase #6	$132.50	6.367%	$140.9363	$140.94	$140.95	$140.90
Purchase #7	$112.94	4.871%	$118.4413	$118.44	$118.45	$118.40
7 purchase totals =	$924.93		$978.4256	$978.43	$978.45	$978.30