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	$171.92	6.735%	$183.4988	$183.50	$183.50	$183.50
Purchase #2	$50.43	7.709%	$54.3176	$54.32	$54.30	$54.30
Purchase #3	$193.81	6.129%	$205.6886	$205.69	$205.70	$205.70
Purchase #4	$78.61	13.850%	$89.4975	$89.50	$89.50	$89.50
Purchase #5	$151.27	6.635%	$161.3068	$161.31	$161.30	$161.30
Purchase #6	$109.65	8.263%	$118.7104	$118.71	$118.70	$118.70
Purchase #7	$117.79	13.769%	$134.0085	$134.01	$134.00	$134.00
7 purchase totals =	$873.48		$947.0282	$947.04	$947.00	$947.00