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	$120.44	6.253%	$127.9711	$127.97	$127.95	$128.00
Purchase #2	$85.66	12.367%	$96.2536	$96.25	$96.25	$96.30
Purchase #3	$127.87	11.328%	$142.3551	$142.36	$142.35	$142.40
Purchase #4	$125.52	10.431%	$138.613	$138.61	$138.60	$138.60
Purchase #5	$211.72	5.588%	$223.5509	$223.55	$223.55	$223.60
Purchase #6	$181.79	7.866%	$196.0896	$196.09	$196.10	$196.10
Purchase #7	$128.49	12.251%	$144.2313	$144.23	$144.25	$144.20
7 purchase totals =	$981.49		$1,069.0646	$1,069.06	$1,069.05	$1,069.20