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	$186.87	9.718%	$205.03	$205.03	$205.05	$205.00
Purchase #2	$184.50	7.566%	$198.4593	$198.46	$198.45	$198.50
Purchase #3	$40.66	6.531%	$43.3155	$43.32	$43.30	$43.30
Purchase #4	$92.25	4.733%	$96.6162	$96.62	$96.60	$96.60
Purchase #5	$181.55	4.676%	$190.0393	$190.04	$190.05	$190.00
Purchase #6	$183.64	13.190%	$207.8621	$207.86	$207.85	$207.90
Purchase #7	$126.63	10.194%	$139.5387	$139.54	$139.55	$139.50
7 purchase totals =	$996.10		$1,080.8611	$1,080.87	$1,080.85	$1,080.80