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	$181.30	7.413%	$194.7398	$194.74	$194.75	$194.70
Purchase #2	$89.53	12.240%	$100.4885	$100.49	$100.50	$100.50
Purchase #3	$136.25	6.315%	$144.8542	$144.85	$144.85	$144.90
Purchase #4	$141.72	10.872%	$157.1278	$157.13	$157.15	$157.10
Purchase #5	$164.43	4.421%	$171.6995	$171.70	$171.70	$171.70
Purchase #6	$130.86	10.730%	$144.9013	$144.90	$144.90	$144.90
Purchase #7	$92.71	13.459%	$105.1878	$105.19	$105.20	$105.20
7 purchase totals =	$936.80		$1,018.9989	$1,019.00	$1,019.05	$1,019.00