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	$57.90	11.774%	$64.7171	$64.72	$64.70	$64.70
Purchase #2	$214.26	8.114%	$231.6451	$231.65	$231.65	$231.60
Purchase #3	$216.46	12.134%	$242.7253	$242.73	$242.75	$242.70
Purchase #4	$43.66	9.868%	$47.9684	$47.97	$47.95	$48.00
Purchase #5	$50.25	7.760%	$54.1494	$54.15	$54.15	$54.10
Purchase #6	$133.30	7.646%	$143.4921	$143.49	$143.50	$143.50
Purchase #7	$89.58	12.623%	$100.8877	$100.89	$100.90	$100.90
7 purchase totals =	$805.41		$885.5851	$885.60	$885.60	$885.50