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	$191.57	7.752%	$206.4205	$206.42	$206.40	$206.40
Purchase #2	$76.48	12.418%	$85.9773	$85.98	$86.00	$86.00
Purchase #3	$17.76	9.105%	$19.377	$19.38	$19.40	$19.40
Purchase #4	$83.76	3.574%	$86.7536	$86.75	$86.75	$86.80
Purchase #5	$104.86	6.679%	$111.8636	$111.86	$111.85	$111.90
Purchase #6	$203.27	3.125%	$209.6222	$209.62	$209.60	$209.60
Purchase #7	$59.27	13.329%	$67.1701	$67.17	$67.15	$67.20
7 purchase totals =	$736.97		$787.1843	$787.18	$787.15	$787.30