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	$95.89	4.428%	$100.136	$100.14	$100.15	$100.10
Purchase #2	$246.52	8.264%	$266.8924	$266.89	$266.90	$266.90
Purchase #3	$104.84	13.119%	$118.594	$118.59	$118.60	$118.60
Purchase #4	$222.64	4.656%	$233.0061	$233.01	$233.00	$233.00
Purchase #5	$212.49	7.735%	$228.9261	$228.93	$228.95	$228.90
Purchase #6	$116.42	9.109%	$127.0247	$127.02	$127.00	$127.00
Purchase #7	$73.62	7.308%	$79.0001	$79.00	$79.00	$79.00
7 purchase totals =	$1,072.42		$1,153.5794	$1,153.58	$1,153.60	$1,153.50