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	$153.49	11.204%	$170.687	$170.69	$170.70	$170.70
Purchase #2	$46.52	12.306%	$52.2448	$52.24	$52.25	$52.20
Purchase #3	$244.61	5.563%	$258.2177	$258.22	$258.20	$258.20
Purchase #4	$39.47	12.149%	$44.2652	$44.27	$44.25	$44.30
Purchase #5	$127.59	13.724%	$145.1005	$145.10	$145.10	$145.10
Purchase #6	$187.39	4.771%	$196.3304	$196.33	$196.35	$196.30
Purchase #7	$125.91	8.535%	$136.6564	$136.66	$136.65	$136.70
7 purchase totals =	$924.98		$1,003.5020	$1,003.51	$1,003.50	$1,003.50