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	$87.95	12.311%	$98.7775	$98.78	$98.80	$98.80
Purchase #2	$235.40	12.822%	$265.583	$265.58	$265.60	$265.60
Purchase #3	$205.77	5.127%	$216.3198	$216.32	$216.30	$216.30
Purchase #4	$74.83	5.597%	$79.0182	$79.02	$79.00	$79.00
Purchase #5	$226.55	5.198%	$238.3261	$238.33	$238.35	$238.30
Purchase #6	$81.73	9.577%	$89.5573	$89.56	$89.55	$89.60
Purchase #7	$107.32	3.123%	$110.6716	$110.67	$110.65	$110.70
7 purchase totals =	$1,019.55		$1,098.2535	$1,098.26	$1,098.25	$1,098.30