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	$91.87	3.323%	$94.9228	$94.92	$94.90	$94.90
Purchase #2	$245.83	4.311%	$256.4277	$256.43	$256.45	$256.40
Purchase #3	$102.96	8.277%	$111.482	$111.48	$111.50	$111.50
Purchase #4	$182.60	12.637%	$205.6752	$205.68	$205.70	$205.70
Purchase #5	$43.30	11.305%	$48.1951	$48.20	$48.20	$48.20
Purchase #6	$96.63	9.375%	$105.6891	$105.69	$105.70	$105.70
Purchase #7	$169.66	5.229%	$178.5315	$178.53	$178.55	$178.50
7 purchase totals =	$932.85		$1,000.9234	$1,000.93	$1,001.00	$1,000.90