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	$136.94	3.590%	$141.8561	$141.86	$141.85	$141.90
Purchase #2	$52.26	13.430%	$59.2785	$59.28	$59.30	$59.30
Purchase #3	$242.48	13.733%	$275.7798	$275.78	$275.80	$275.80
Purchase #4	$24.53	3.678%	$25.4322	$25.43	$25.45	$25.40
Purchase #5	$82.88	9.277%	$90.5688	$90.57	$90.55	$90.60
Purchase #6	$170.26	13.802%	$193.7593	$193.76	$193.75	$193.80
Purchase #7	$20.27	13.483%	$23.003	$23.00	$23.00	$23.00
7 purchase totals =	$729.62		$809.6777	$809.68	$809.70	$809.80