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	$195.40	7.279%	$209.6232	$209.62	$209.60	$209.60
Purchase #2	$105.54	3.119%	$108.8318	$108.83	$108.85	$108.80
Purchase #3	$37.41	4.518%	$39.1002	$39.10	$39.10	$39.10
Purchase #4	$180.64	10.300%	$199.2459	$199.25	$199.25	$199.20
Purchase #5	$51.99	7.763%	$56.026	$56.03	$56.05	$56.00
Purchase #6	$104.94	6.369%	$111.6236	$111.62	$111.60	$111.60
Purchase #7	$190.91	10.329%	$210.6291	$210.63	$210.65	$210.60
7 purchase totals =	$866.83		$935.0798	$935.08	$935.10	$934.90