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	$62.83	13.578%	$71.3611	$71.36	$71.35	$71.40
Purchase #2	$98.50	11.244%	$109.5753	$109.58	$109.60	$109.60
Purchase #3	$70.28	9.462%	$76.9299	$76.93	$76.95	$76.90
Purchase #4	$132.39	3.109%	$136.506	$136.51	$136.50	$136.50
Purchase #5	$239.56	13.308%	$271.4406	$271.44	$271.45	$271.40
Purchase #6	$170.94	11.425%	$190.4699	$190.47	$190.45	$190.50
Purchase #7	$49.46	11.787%	$55.2899	$55.29	$55.30	$55.30
7 purchase totals =	$823.96		$911.5727	$911.58	$911.60	$911.60