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	$157.59	4.365%	$164.4688	$164.47	$164.45	$164.50
Purchase #2	$134.67	6.477%	$143.3926	$143.39	$143.40	$143.40
Purchase #3	$19.74	5.161%	$20.7588	$20.76	$20.75	$20.80
Purchase #4	$151.27	9.164%	$165.1324	$165.13	$165.15	$165.10
Purchase #5	$52.43	4.230%	$54.6478	$54.65	$54.65	$54.60
Purchase #6	$160.75	12.232%	$180.4129	$180.41	$180.40	$180.40
Purchase #7	$187.79	9.473%	$205.5793	$205.58	$205.60	$205.60
7 purchase totals =	$864.24		$934.3926	$934.39	$934.40	$934.40