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	$167.66	9.326%	$183.296	$183.30	$183.30	$183.30
Purchase #2	$71.94	8.558%	$78.0966	$78.10	$78.10	$78.10
Purchase #3	$236.86	12.464%	$266.3822	$266.38	$266.40	$266.40
Purchase #4	$154.78	11.464%	$172.524	$172.52	$172.50	$172.50
Purchase #5	$169.41	11.678%	$189.1937	$189.19	$189.20	$189.20
Purchase #6	$141.49	4.794%	$148.273	$148.27	$148.25	$148.30
Purchase #7	$45.40	7.808%	$48.9448	$48.94	$48.95	$48.90
7 purchase totals =	$987.54		$1,086.7103	$1,086.70	$1,086.70	$1,086.70