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	$99.42	12.766%	$112.112	$112.11	$112.10	$112.10
Purchase #2	$205.40	11.370%	$228.754	$228.75	$228.75	$228.80
Purchase #3	$116.29	9.309%	$127.1154	$127.12	$127.10	$127.10
Purchase #4	$47.33	8.110%	$51.1685	$51.17	$51.15	$51.20
Purchase #5	$247.98	9.465%	$271.4513	$271.45	$271.45	$271.50
Purchase #6	$39.30	11.371%	$43.7688	$43.77	$43.75	$43.80
Purchase #7	$159.52	13.271%	$180.6899	$180.69	$180.70	$180.70
7 purchase totals =	$915.24		$1,015.0599	$1,015.06	$1,015.00	$1,015.20