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	$226.77	5.337%	$238.8727	$238.87	$238.85	$238.90
Purchase #2	$39.90	8.408%	$43.2548	$43.25	$43.25	$43.30
Purchase #3	$72.37	8.174%	$78.2855	$78.29	$78.30	$78.30
Purchase #4	$76.95	4.769%	$80.6197	$80.62	$80.60	$80.60
Purchase #5	$190.82	9.840%	$209.5967	$209.60	$209.60	$209.60
Purchase #6	$167.49	11.798%	$187.2505	$187.25	$187.25	$187.30
Purchase #7	$128.62	4.207%	$134.031	$134.03	$134.05	$134.00
7 purchase totals =	$902.92		$971.9109	$971.91	$971.90	$972.00