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	$177.81	5.173%	$187.0081	$187.01	$187.00	$187.00
Purchase #2	$179.53	6.194%	$190.6501	$190.65	$190.65	$190.70
Purchase #3	$47.35	9.266%	$51.7375	$51.74	$51.75	$51.70
Purchase #4	$212.61	13.637%	$241.6036	$241.60	$241.60	$241.60
Purchase #5	$38.25	12.800%	$43.146	$43.15	$43.15	$43.10
Purchase #6	$72.40	8.813%	$78.7806	$78.78	$78.80	$78.80
Purchase #7	$102.91	4.485%	$107.5255	$107.53	$107.55	$107.50
7 purchase totals =	$830.86		$900.4514	$900.46	$900.50	$900.40