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	$65.65	10.592%	$72.6036	$72.60	$72.60	$72.60
Purchase #2	$48.38	9.601%	$53.025	$53.03	$53.05	$53.00
Purchase #3	$109.92	3.558%	$113.831	$113.83	$113.85	$113.80
Purchase #4	$173.43	6.544%	$184.7793	$184.78	$184.80	$184.80
Purchase #5	$172.90	7.153%	$185.2675	$185.27	$185.25	$185.30
Purchase #6	$118.28	8.373%	$128.1836	$128.18	$128.20	$128.20
Purchase #7	$53.93	4.503%	$56.3585	$56.36	$56.35	$56.40
7 purchase totals =	$742.49		$794.0485	$794.05	$794.10	$794.10