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	$193.42	13.317%	$219.1777	$219.18	$219.20	$219.20
Purchase #2	$134.62	12.265%	$151.1311	$151.13	$151.15	$151.10
Purchase #3	$39.67	7.729%	$42.7361	$42.74	$42.75	$42.70
Purchase #4	$71.70	8.805%	$78.0132	$78.01	$78.00	$78.00
Purchase #5	$133.82	11.268%	$148.8988	$148.90	$148.90	$148.90
Purchase #6	$248.91	7.115%	$266.6199	$266.62	$266.60	$266.60
Purchase #7	$177.69	10.564%	$196.4612	$196.46	$196.45	$196.50
7 purchase totals =	$999.83		$1,103.0380	$1,103.04	$1,103.05	$1,103.00