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	$211.84	6.201%	$224.9762	$224.98	$225.00	$225.00
Purchase #2	$100.43	8.638%	$109.1051	$109.11	$109.10	$109.10
Purchase #3	$171.70	9.293%	$187.6561	$187.66	$187.65	$187.70
Purchase #4	$38.52	13.325%	$43.6528	$43.65	$43.65	$43.70
Purchase #5	$250.50	4.758%	$262.4188	$262.42	$262.40	$262.40
Purchase #6	$209.64	7.196%	$224.7257	$224.73	$224.75	$224.70
Purchase #7	$80.97	10.388%	$89.3812	$89.38	$89.40	$89.40
7 purchase totals =	$1,063.60		$1,141.9159	$1,141.93	$1,141.95	$1,142.00