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	$213.88	8.873%	$232.8576	$232.86	$232.85	$232.90
Purchase #2	$144.63	7.494%	$155.4686	$155.47	$155.45	$155.50
Purchase #3	$200.59	12.243%	$225.1482	$225.15	$225.15	$225.10
Purchase #4	$185.96	3.426%	$192.331	$192.33	$192.35	$192.30
Purchase #5	$159.91	12.340%	$179.6429	$179.64	$179.65	$179.60
Purchase #6	$200.87	11.338%	$223.6446	$223.64	$223.65	$223.60
Purchase #7	$20.72	3.867%	$21.5212	$21.52	$21.50	$21.50
7 purchase totals =	$1,126.56		$1,230.6141	$1,230.61	$1,230.60	$1,230.50