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	$65.67	13.153%	$74.3076	$74.31	$74.30	$74.30
Purchase #2	$75.84	3.587%	$78.5604	$78.56	$78.55	$78.60
Purchase #3	$194.94	10.364%	$215.1436	$215.14	$215.15	$215.10
Purchase #4	$59.25	4.713%	$62.0425	$62.04	$62.05	$62.00
Purchase #5	$80.44	6.678%	$85.8118	$85.81	$85.80	$85.80
Purchase #6	$88.38	8.143%	$95.5768	$95.58	$95.60	$95.60
Purchase #7	$151.55	13.271%	$171.6622	$171.66	$171.65	$171.70
7 purchase totals =	$716.07		$783.1049	$783.10	$783.10	$783.10