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	$78.70	9.735%	$86.3614	$86.36	$86.35	$86.40
Purchase #2	$151.78	6.776%	$162.0646	$162.06	$162.05	$162.10
Purchase #3	$24.45	4.631%	$25.5823	$25.58	$25.60	$25.60
Purchase #4	$31.50	6.751%	$33.6266	$33.63	$33.65	$33.60
Purchase #5	$171.76	8.236%	$185.9062	$185.91	$185.90	$185.90
Purchase #6	$173.25	12.448%	$194.8162	$194.82	$194.80	$194.80
Purchase #7	$7.78	4.725%	$8.1476	$8.15	$8.15	$8.10
7 purchase totals =	$639.22		$696.5049	$696.51	$696.50	$696.50