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	$50.27	7.860%	$54.2212	$54.22	$54.20	$54.20
Purchase #2	$16.76	13.719%	$19.0593	$19.06	$19.05	$19.10
Purchase #3	$243.82	11.781%	$272.5444	$272.54	$272.55	$272.50
Purchase #4	$40.68	6.782%	$43.4389	$43.44	$43.45	$43.40
Purchase #5	$152.51	4.175%	$158.8773	$158.88	$158.90	$158.90
Purchase #6	$216.46	13.478%	$245.6345	$245.63	$245.65	$245.60
Purchase #7	$218.43	13.291%	$247.4615	$247.46	$247.45	$247.50
7 purchase totals =	$938.93		$1,041.2371	$1,041.23	$1,041.25	$1,041.20