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	$106.80	6.806%	$114.0688	$114.07	$114.05	$114.10
Purchase #2	$157.44	13.850%	$179.2454	$179.25	$179.25	$179.20
Purchase #3	$121.61	8.437%	$131.8702	$131.87	$131.85	$131.90
Purchase #4	$134.82	12.520%	$151.6995	$151.70	$151.70	$151.70
Purchase #5	$230.48	5.218%	$242.5064	$242.51	$242.50	$242.50
Purchase #6	$101.90	9.787%	$111.873	$111.87	$111.85	$111.90
Purchase #7	$69.73	8.439%	$75.6145	$75.61	$75.60	$75.60
7 purchase totals =	$922.78		$1,006.8778	$1,006.88	$1,006.80	$1,006.90