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	$167.27	5.379%	$176.2675	$176.27	$176.25	$176.30
Purchase #2	$109.55	4.535%	$114.5181	$114.52	$114.50	$114.50
Purchase #3	$99.85	6.160%	$106.0008	$106.00	$106.00	$106.00
Purchase #4	$12.83	11.394%	$14.2919	$14.29	$14.30	$14.30
Purchase #5	$91.28	10.174%	$100.5668	$100.57	$100.55	$100.60
Purchase #6	$39.96	12.866%	$45.1013	$45.10	$45.10	$45.10
Purchase #7	$22.96	10.216%	$25.3056	$25.31	$25.30	$25.30
7 purchase totals =	$543.70		$582.0520	$582.06	$582.00	$582.10