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	$235.67	8.335%	$255.3131	$255.31	$255.30	$255.30
Purchase #2	$19.30	13.621%	$21.9289	$21.93	$21.95	$21.90
Purchase #3	$233.61	9.868%	$256.6626	$256.66	$256.65	$256.70
Purchase #4	$198.44	3.404%	$205.1949	$205.19	$205.20	$205.20
Purchase #5	$189.75	4.591%	$198.4614	$198.46	$198.45	$198.50
Purchase #6	$5.83	10.229%	$6.4264	$6.43	$6.45	$6.40
Purchase #7	$85.82	3.280%	$88.6349	$88.63	$88.65	$88.60
7 purchase totals =	$968.42		$1,032.6222	$1,032.61	$1,032.65	$1,032.60