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	$215.84	8.354%	$233.8713	$233.87	$233.85	$233.90
Purchase #2	$102.97	10.367%	$113.6449	$113.64	$113.65	$113.60
Purchase #3	$209.99	6.371%	$223.3685	$223.37	$223.35	$223.40
Purchase #4	$112.88	13.287%	$127.8784	$127.88	$127.90	$127.90
Purchase #5	$48.29	7.829%	$52.0706	$52.07	$52.05	$52.10
Purchase #6	$214.68	4.313%	$223.9391	$223.94	$223.95	$223.90
Purchase #7	$93.27	10.738%	$103.2853	$103.29	$103.30	$103.30
7 purchase totals =	$997.92		$1,078.0581	$1,078.06	$1,078.05	$1,078.10