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	$71.31	7.271%	$76.495	$76.50	$76.50	$76.50
Purchase #2	$46.90	3.647%	$48.6104	$48.61	$48.60	$48.60
Purchase #3	$55.32	4.185%	$57.6351	$57.64	$57.65	$57.60
Purchase #4	$80.86	3.627%	$83.7928	$83.79	$83.80	$83.80
Purchase #5	$165.93	4.717%	$173.7569	$173.76	$173.75	$173.80
Purchase #6	$37.99	6.474%	$40.4495	$40.45	$40.45	$40.40
Purchase #7	$211.40	13.745%	$240.4569	$240.46	$240.45	$240.50
7 purchase totals =	$669.71		$721.1966	$721.21	$721.20	$721.20