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	$181.49	5.163%	$190.8603	$190.86	$190.85	$190.90
Purchase #2	$49.89	3.276%	$51.5244	$51.52	$51.50	$51.50
Purchase #3	$9.96	5.663%	$10.524	$10.52	$10.50	$10.50
Purchase #4	$239.61	4.211%	$249.7	$249.70	$249.70	$249.70
Purchase #5	$208.88	13.208%	$236.4689	$236.47	$236.45	$236.50
Purchase #6	$129.78	9.724%	$142.3998	$142.40	$142.40	$142.40
Purchase #7	$115.90	9.798%	$127.2559	$127.26	$127.25	$127.30
7 purchase totals =	$935.51		$1,008.7333	$1,008.73	$1,008.65	$1,008.80