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	$62.30	5.364%	$65.6418	$65.64	$65.65	$65.60
Purchase #2	$36.29	8.666%	$39.4349	$39.43	$39.45	$39.40
Purchase #3	$18.31	4.380%	$19.112	$19.11	$19.10	$19.10
Purchase #4	$172.94	9.439%	$189.2638	$189.26	$189.25	$189.30
Purchase #5	$173.86	10.394%	$191.931	$191.93	$191.95	$191.90
Purchase #6	$232.78	3.689%	$241.3673	$241.37	$241.35	$241.40
Purchase #7	$39.85	8.178%	$43.1089	$43.11	$43.10	$43.10
7 purchase totals =	$736.33		$789.8597	$789.85	$789.85	$789.80