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	$176.67	7.745%	$190.3531	$190.35	$190.35	$190.40
Purchase #2	$9.72	8.239%	$10.5208	$10.52	$10.50	$10.50
Purchase #3	$239.50	12.792%	$270.1368	$270.14	$270.15	$270.10
Purchase #4	$120.67	6.269%	$128.2348	$128.23	$128.25	$128.20
Purchase #5	$134.43	3.530%	$139.1754	$139.18	$139.20	$139.20
Purchase #6	$66.41	8.395%	$71.9851	$71.99	$72.00	$72.00
Purchase #7	$215.89	11.672%	$241.0887	$241.09	$241.10	$241.10
7 purchase totals =	$963.29		$1,051.4947	$1,051.50	$1,051.55	$1,051.50