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	$205.77	13.814%	$234.1951	$234.20	$234.20	$234.20
Purchase #2	$134.26	12.325%	$150.8075	$150.81	$150.80	$150.80
Purchase #3	$54.50	8.728%	$59.2568	$59.26	$59.25	$59.30
Purchase #4	$139.56	8.587%	$151.544	$151.54	$151.55	$151.50
Purchase #5	$19.38	13.762%	$22.0471	$22.05	$22.05	$22.00
Purchase #6	$39.58	12.554%	$44.5489	$44.55	$44.55	$44.50
Purchase #7	$99.99	11.650%	$111.6388	$111.64	$111.65	$111.60
7 purchase totals =	$693.04		$774.0382	$774.05	$774.05	$773.90