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	$140.70	10.577%	$155.5818	$155.58	$155.60	$155.60
Purchase #2	$171.87	10.724%	$190.3013	$190.30	$190.30	$190.30
Purchase #3	$39.32	10.143%	$43.3082	$43.31	$43.30	$43.30
Purchase #4	$154.91	8.428%	$167.9658	$167.97	$167.95	$168.00
Purchase #5	$195.57	13.215%	$221.4146	$221.41	$221.40	$221.40
Purchase #6	$155.54	13.578%	$176.6592	$176.66	$176.65	$176.70
Purchase #7	$159.92	7.863%	$172.4945	$172.49	$172.50	$172.50
7 purchase totals =	$1,017.83		$1,127.7254	$1,127.72	$1,127.70	$1,127.80