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	$161.63	13.606%	$183.6214	$183.62	$183.60	$183.60
Purchase #2	$47.96	13.618%	$54.4912	$54.49	$54.50	$54.50
Purchase #3	$44.51	5.810%	$47.096	$47.10	$47.10	$47.10
Purchase #4	$134.88	3.285%	$139.3108	$139.31	$139.30	$139.30
Purchase #5	$247.25	9.127%	$269.8165	$269.82	$269.80	$269.80
Purchase #6	$7.59	6.483%	$8.0821	$8.08	$8.10	$8.10
Purchase #7	$37.37	13.742%	$42.5054	$42.51	$42.50	$42.50
7 purchase totals =	$681.19		$744.9234	$744.93	$744.90	$744.90