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	$189.64	7.619%	$204.0887	$204.09	$204.10	$204.10
Purchase #2	$221.26	9.530%	$242.3461	$242.35	$242.35	$242.30
Purchase #3	$161.33	10.710%	$178.6084	$178.61	$178.60	$178.60
Purchase #4	$34.52	7.840%	$37.2264	$37.23	$37.25	$37.20
Purchase #5	$123.91	3.244%	$127.9296	$127.93	$127.95	$127.90
Purchase #6	$194.46	5.766%	$205.6726	$205.67	$205.65	$205.70
Purchase #7	$131.94	6.408%	$140.3947	$140.39	$140.40	$140.40
7 purchase totals =	$1,057.06		$1,136.2665	$1,136.27	$1,136.30	$1,136.20