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	$183.84	4.233%	$191.6219	$191.62	$191.60	$191.60
Purchase #2	$68.39	13.216%	$77.4284	$77.43	$77.45	$77.40
Purchase #3	$178.33	3.541%	$184.6447	$184.64	$184.65	$184.60
Purchase #4	$109.89	8.545%	$119.2801	$119.28	$119.30	$119.30
Purchase #5	$191.59	13.425%	$217.311	$217.31	$217.30	$217.30
Purchase #6	$76.71	12.592%	$86.3693	$86.37	$86.35	$86.40
Purchase #7	$195.85	5.667%	$206.9488	$206.95	$206.95	$206.90
7 purchase totals =	$1,004.60		$1,083.6042	$1,083.60	$1,083.60	$1,083.50