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	$113.44	6.105%	$120.3655	$120.37	$120.35	$120.40
Purchase #2	$234.40	3.425%	$242.4282	$242.43	$242.45	$242.40
Purchase #3	$58.53	6.313%	$62.225	$62.23	$62.25	$62.20
Purchase #4	$91.31	10.175%	$100.6008	$100.60	$100.60	$100.60
Purchase #5	$24.74	11.699%	$27.6343	$27.63	$27.65	$27.60
Purchase #6	$161.39	6.509%	$171.8949	$171.89	$171.90	$171.90
Purchase #7	$131.70	5.655%	$139.1476	$139.15	$139.15	$139.10
7 purchase totals =	$815.51		$864.2963	$864.30	$864.35	$864.20