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	$155.54	6.633%	$165.857	$165.86	$165.85	$165.90
Purchase #2	$185.67	10.612%	$205.3733	$205.37	$205.35	$205.40
Purchase #3	$139.81	8.476%	$151.6603	$151.66	$151.65	$151.70
Purchase #4	$198.91	7.235%	$213.3011	$213.30	$213.30	$213.30
Purchase #5	$97.69	11.820%	$109.237	$109.24	$109.25	$109.20
Purchase #6	$14.60	11.413%	$16.2663	$16.27	$16.25	$16.30
Purchase #7	$185.85	13.275%	$210.5216	$210.52	$210.50	$210.50
7 purchase totals =	$978.07		$1,072.2166	$1,072.22	$1,072.15	$1,072.30