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	$51.57	4.571%	$53.9273	$53.93	$53.95	$53.90
Purchase #2	$100.43	13.595%	$114.0835	$114.08	$114.10	$114.10
Purchase #3	$141.65	6.706%	$151.149	$151.15	$151.15	$151.10
Purchase #4	$49.85	5.161%	$52.4228	$52.42	$52.40	$52.40
Purchase #5	$172.57	8.547%	$187.3196	$187.32	$187.30	$187.30
Purchase #6	$92.74	13.573%	$105.3276	$105.33	$105.35	$105.30
Purchase #7	$150.32	13.130%	$170.057	$170.06	$170.05	$170.10
7 purchase totals =	$759.13		$834.2868	$834.29	$834.30	$834.20