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	$76.61	7.673%	$82.4883	$82.49	$82.50	$82.50
Purchase #2	$98.57	6.138%	$104.6202	$104.62	$104.60	$104.60
Purchase #3	$107.84	9.568%	$118.1581	$118.16	$118.15	$118.20
Purchase #4	$193.28	3.423%	$199.896	$199.90	$199.90	$199.90
Purchase #5	$174.72	5.459%	$184.258	$184.26	$184.25	$184.30
Purchase #6	$67.99	7.240%	$72.9125	$72.91	$72.90	$72.90
Purchase #7	$18.57	13.426%	$21.0632	$21.06	$21.05	$21.10
7 purchase totals =	$737.58		$783.3963	$783.40	$783.35	$783.50