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	$161.85	4.805%	$169.6269	$169.63	$169.65	$169.60
Purchase #2	$62.85	11.504%	$70.0803	$70.08	$70.10	$70.10
Purchase #3	$139.86	5.534%	$147.5999	$147.60	$147.60	$147.60
Purchase #4	$52.32	3.840%	$54.3291	$54.33	$54.35	$54.30
Purchase #5	$56.73	4.491%	$59.2777	$59.28	$59.30	$59.30
Purchase #6	$158.64	12.694%	$178.7778	$178.78	$178.80	$178.80
Purchase #7	$97.88	12.337%	$109.9555	$109.96	$109.95	$110.00
7 purchase totals =	$730.13		$789.6472	$789.66	$789.75	$789.70