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	$226.86	8.382%	$245.8754	$245.88	$245.90	$245.90
Purchase #2	$120.37	11.704%	$134.4581	$134.46	$134.45	$134.50
Purchase #3	$145.53	9.131%	$158.8183	$158.82	$158.80	$158.80
Purchase #4	$46.79	8.535%	$50.7835	$50.78	$50.80	$50.80
Purchase #5	$181.25	5.142%	$190.5699	$190.57	$190.55	$190.60
Purchase #6	$110.38	8.102%	$119.323	$119.32	$119.30	$119.30
Purchase #7	$187.65	9.556%	$205.5818	$205.58	$205.60	$205.60
7 purchase totals =	$1,018.83		$1,105.4100	$1,105.41	$1,105.40	$1,105.50