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	$100.26	10.717%	$111.0049	$111.00	$111.00	$111.00
Purchase #2	$233.36	5.346%	$245.8354	$245.84	$245.85	$245.80
Purchase #3	$181.49	5.736%	$191.9003	$191.90	$191.90	$191.90
Purchase #4	$183.47	13.323%	$207.9137	$207.91	$207.90	$207.90
Purchase #5	$126.98	3.676%	$131.6478	$131.65	$131.65	$131.60
Purchase #6	$162.39	13.493%	$184.3013	$184.30	$184.30	$184.30
Purchase #7	$63.33	11.660%	$70.7143	$70.71	$70.70	$70.70
7 purchase totals =	$1,051.28		$1,143.3177	$1,143.31	$1,143.30	$1,143.20