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	$184.76	3.180%	$190.6354	$190.64	$190.65	$190.60
Purchase #2	$46.85	12.828%	$52.8599	$52.86	$52.85	$52.90
Purchase #3	$42.52	7.254%	$45.6044	$45.60	$45.60	$45.60
Purchase #4	$17.83	11.106%	$19.8102	$19.81	$19.80	$19.80
Purchase #5	$35.32	8.749%	$38.4101	$38.41	$38.40	$38.40
Purchase #6	$90.73	4.681%	$94.9771	$94.98	$95.00	$95.00
Purchase #7	$194.98	11.681%	$217.7556	$217.76	$217.75	$217.80
7 purchase totals =	$612.99		$660.0527	$660.06	$660.05	$660.10