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	$67.41	7.830%	$72.6882	$72.69	$72.70	$72.70
Purchase #2	$62.45	5.242%	$65.7236	$65.72	$65.70	$65.70
Purchase #3	$105.30	6.208%	$111.837	$111.84	$111.85	$111.80
Purchase #4	$249.45	12.461%	$280.534	$280.53	$280.55	$280.50
Purchase #5	$43.38	13.763%	$49.3504	$49.35	$49.35	$49.40
Purchase #6	$161.86	13.674%	$183.9927	$183.99	$184.00	$184.00
Purchase #7	$236.63	6.257%	$251.4359	$251.44	$251.45	$251.40
7 purchase totals =	$926.48		$1,015.5618	$1,015.56	$1,015.60	$1,015.50