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	$224.51	4.733%	$235.1361	$235.14	$235.15	$235.10
Purchase #2	$139.45	6.408%	$148.386	$148.39	$148.40	$148.40
Purchase #3	$59.41	12.169%	$66.6396	$66.64	$66.65	$66.60
Purchase #4	$91.32	4.597%	$95.518	$95.52	$95.50	$95.50
Purchase #5	$184.50	9.806%	$202.5921	$202.59	$202.60	$202.60
Purchase #6	$187.55	12.223%	$210.4742	$210.47	$210.45	$210.50
Purchase #7	$89.67	10.496%	$99.0818	$99.08	$99.10	$99.10
7 purchase totals =	$976.41		$1,057.8278	$1,057.83	$1,057.85	$1,057.80