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	$97.85	13.720%	$111.275	$111.28	$111.30	$111.30
Purchase #2	$165.34	12.513%	$186.029	$186.03	$186.05	$186.00
Purchase #3	$186.25	4.230%	$194.1284	$194.13	$194.15	$194.10
Purchase #4	$217.32	3.685%	$225.3282	$225.33	$225.35	$225.30
Purchase #5	$41.85	9.803%	$45.9526	$45.95	$45.95	$46.00
Purchase #6	$55.82	12.437%	$62.7623	$62.76	$62.75	$62.80
Purchase #7	$32.43	3.560%	$33.5845	$33.58	$33.60	$33.60
7 purchase totals =	$796.86		$859.0600	$859.06	$859.15	$859.10