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	$151.79	5.320%	$159.8652	$159.87	$159.85	$159.90
Purchase #2	$45.47	12.700%	$51.2447	$51.24	$51.25	$51.20
Purchase #3	$55.44	5.371%	$58.4177	$58.42	$58.40	$58.40
Purchase #4	$19.57	10.466%	$21.6182	$21.62	$21.60	$21.60
Purchase #5	$41.92	4.639%	$43.8647	$43.86	$43.85	$43.90
Purchase #6	$164.64	5.130%	$173.086	$173.09	$173.10	$173.10
Purchase #7	$23.91	13.659%	$27.1759	$27.18	$27.20	$27.20
7 purchase totals =	$502.74		$535.2724	$535.28	$535.25	$535.30