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	$118.46	4.590%	$123.8973	$123.90	$123.90	$123.90
Purchase #2	$63.98	5.329%	$67.3895	$67.39	$67.40	$67.40
Purchase #3	$163.33	6.283%	$173.592	$173.59	$173.60	$173.60
Purchase #4	$72.31	13.228%	$81.8752	$81.88	$81.90	$81.90
Purchase #5	$10.81	3.179%	$11.1536	$11.15	$11.15	$11.20
Purchase #6	$174.55	9.381%	$190.9245	$190.92	$190.90	$190.90
Purchase #7	$109.93	9.613%	$120.4976	$120.50	$120.50	$120.50
7 purchase totals =	$713.37		$769.3297	$769.33	$769.35	$769.40