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	$65.54	3.838%	$68.0554	$68.06	$68.05	$68.10
Purchase #2	$87.90	4.164%	$91.5602	$91.56	$91.55	$91.60
Purchase #3	$86.86	3.401%	$89.8141	$89.81	$89.80	$89.80
Purchase #4	$229.32	12.126%	$257.1273	$257.13	$257.15	$257.10
Purchase #5	$87.58	4.630%	$91.635	$91.64	$91.65	$91.60
Purchase #6	$17.92	3.121%	$18.4793	$18.48	$18.50	$18.50
Purchase #7	$87.40	3.169%	$90.1697	$90.17	$90.15	$90.20
7 purchase totals =	$662.52		$706.8410	$706.85	$706.85	$706.90