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	$132.48	7.731%	$142.722	$142.72	$142.70	$142.70
Purchase #2	$39.30	8.188%	$42.5179	$42.52	$42.50	$42.50
Purchase #3	$50.48	13.437%	$57.263	$57.26	$57.25	$57.30
Purchase #4	$97.89	7.211%	$104.9488	$104.95	$104.95	$104.90
Purchase #5	$131.84	12.673%	$148.5481	$148.55	$148.55	$148.50
Purchase #6	$143.92	7.409%	$154.583	$154.58	$154.60	$154.60
Purchase #7	$70.59	11.471%	$78.6874	$78.69	$78.70	$78.70
7 purchase totals =	$666.50		$729.2702	$729.27	$729.25	$729.20