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	$122.54	4.434%	$127.9734	$127.97	$127.95	$128.00
Purchase #2	$96.47	10.596%	$106.692	$106.69	$106.70	$106.70
Purchase #3	$117.87	4.405%	$123.0622	$123.06	$123.05	$123.10
Purchase #4	$178.92	3.419%	$185.0373	$185.04	$185.05	$185.00
Purchase #5	$63.58	6.332%	$67.6059	$67.61	$67.60	$67.60
Purchase #6	$88.67	8.705%	$96.3887	$96.39	$96.40	$96.40
Purchase #7	$181.51	12.675%	$204.5164	$204.52	$204.50	$204.50
7 purchase totals =	$849.56		$911.2759	$911.28	$911.25	$911.30