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	$223.27	10.664%	$247.0795	$247.08	$247.10	$247.10
Purchase #2	$49.97	12.191%	$56.0618	$56.06	$56.05	$56.10
Purchase #3	$179.97	4.462%	$188.0003	$188.00	$188.00	$188.00
Purchase #4	$127.30	12.274%	$142.9248	$142.92	$142.90	$142.90
Purchase #5	$41.37	5.666%	$43.714	$43.71	$43.70	$43.70
Purchase #6	$194.98	8.426%	$211.409	$211.41	$211.40	$211.40
Purchase #7	$244.70	3.537%	$253.355	$253.36	$253.35	$253.40
7 purchase totals =	$1,061.56		$1,142.5444	$1,142.54	$1,142.50	$1,142.60