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	$146.94	9.168%	$160.4115	$160.41	$160.40	$160.40
Purchase #2	$151.62	3.589%	$157.0616	$157.06	$157.05	$157.10
Purchase #3	$70.32	12.731%	$79.2724	$79.27	$79.25	$79.30
Purchase #4	$102.72	11.785%	$114.8256	$114.83	$114.85	$114.80
Purchase #5	$13.63	4.778%	$14.2812	$14.28	$14.30	$14.30
Purchase #6	$81.50	9.653%	$89.3672	$89.37	$89.35	$89.40
Purchase #7	$97.74	6.730%	$104.3179	$104.32	$104.30	$104.30
7 purchase totals =	$664.47		$719.5374	$719.54	$719.50	$719.60