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	$250.58	13.693%	$284.8919	$284.89	$284.90	$284.90
Purchase #2	$192.51	6.626%	$205.2657	$205.27	$205.25	$205.30
Purchase #3	$124.63	13.634%	$141.6221	$141.62	$141.60	$141.60
Purchase #4	$39.36	11.185%	$43.7624	$43.76	$43.75	$43.80
Purchase #5	$52.74	7.494%	$56.6923	$56.69	$56.70	$56.70
Purchase #6	$134.30	6.846%	$143.4942	$143.49	$143.50	$143.50
Purchase #7	$175.41	6.743%	$187.2379	$187.24	$187.25	$187.20
7 purchase totals =	$969.53		$1,062.9665	$1,062.96	$1,062.95	$1,063.00