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	$91.46	8.730%	$99.4445	$99.44	$99.45	$99.40
Purchase #2	$116.39	5.752%	$123.0848	$123.08	$123.10	$123.10
Purchase #3	$10.94	11.729%	$12.2232	$12.22	$12.20	$12.20
Purchase #4	$142.95	9.517%	$156.5546	$156.55	$156.55	$156.60
Purchase #5	$166.57	10.176%	$183.5202	$183.52	$183.50	$183.50
Purchase #6	$106.39	7.171%	$114.0192	$114.02	$114.00	$114.00
Purchase #7	$109.91	7.472%	$118.1225	$118.12	$118.10	$118.10
7 purchase totals =	$744.61		$806.9690	$806.95	$806.90	$806.90