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	$186.29	6.866%	$199.0807	$199.08	$199.10	$199.10
Purchase #2	$89.85	9.700%	$98.5655	$98.57	$98.55	$98.60
Purchase #3	$215.63	4.242%	$224.777	$224.78	$224.80	$224.80
Purchase #4	$117.89	4.554%	$123.2587	$123.26	$123.25	$123.30
Purchase #5	$142.79	10.267%	$157.4502	$157.45	$157.45	$157.50
Purchase #6	$137.65	3.464%	$142.4182	$142.42	$142.40	$142.40
Purchase #7	$242.76	4.724%	$254.228	$254.23	$254.25	$254.20
7 purchase totals =	$1,132.86		$1,199.7783	$1,199.79	$1,199.80	$1,199.90