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	$155.30	7.778%	$167.3792	$167.38	$167.40	$167.40
Purchase #2	$50.89	10.118%	$56.0391	$56.04	$56.05	$56.00
Purchase #3	$209.88	13.527%	$238.2705	$238.27	$238.25	$238.30
Purchase #4	$247.51	7.548%	$266.1921	$266.19	$266.20	$266.20
Purchase #5	$203.82	5.695%	$215.4275	$215.43	$215.45	$215.40
Purchase #6	$50.87	7.317%	$54.5922	$54.59	$54.60	$54.60
Purchase #7	$204.47	7.178%	$219.1469	$219.15	$219.15	$219.10
7 purchase totals =	$1,122.74		$1,217.0475	$1,217.05	$1,217.10	$1,217.00