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	$144.49	9.731%	$158.5503	$158.55	$158.55	$158.60
Purchase #2	$13.56	7.471%	$14.5731	$14.57	$14.55	$14.60
Purchase #3	$124.46	8.277%	$134.7616	$134.76	$134.75	$134.80
Purchase #4	$136.90	3.809%	$142.1145	$142.11	$142.10	$142.10
Purchase #5	$59.42	13.668%	$67.5415	$67.54	$67.55	$67.50
Purchase #6	$118.25	8.309%	$128.0754	$128.08	$128.10	$128.10
Purchase #7	$155.86	13.658%	$177.1474	$177.15	$177.15	$177.10
7 purchase totals =	$752.94		$822.7638	$822.76	$822.75	$822.80