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	$171.60	11.253%	$190.9101	$190.91	$190.90	$190.90
Purchase #2	$48.97	9.331%	$53.5394	$53.54	$53.55	$53.50
Purchase #3	$5.42	3.376%	$5.603	$5.60	$5.60	$5.60
Purchase #4	$171.67	9.240%	$187.5323	$187.53	$187.55	$187.50
Purchase #5	$222.63	13.460%	$252.596	$252.60	$252.60	$252.60
Purchase #6	$144.31	7.477%	$155.1001	$155.10	$155.10	$155.10
Purchase #7	$77.56	3.718%	$80.4437	$80.44	$80.45	$80.40
7 purchase totals =	$842.16		$925.7246	$925.72	$925.75	$925.60