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	$208.52	10.766%	$230.9693	$230.97	$230.95	$231.00
Purchase #2	$96.81	8.343%	$104.8869	$104.89	$104.90	$104.90
Purchase #3	$183.65	3.482%	$190.0447	$190.04	$190.05	$190.00
Purchase #4	$213.39	4.511%	$223.016	$223.02	$223.00	$223.00
Purchase #5	$48.32	13.464%	$54.8258	$54.83	$54.85	$54.80
Purchase #6	$204.49	5.268%	$215.2625	$215.26	$215.25	$215.30
Purchase #7	$94.85	4.814%	$99.4161	$99.42	$99.40	$99.40
7 purchase totals =	$1,050.03		$1,118.4213	$1,118.43	$1,118.40	$1,118.40