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	$227.25	6.868%	$242.8575	$242.86	$242.85	$242.90
Purchase #2	$129.96	9.292%	$142.0359	$142.04	$142.05	$142.00
Purchase #3	$207.55	3.129%	$214.0442	$214.04	$214.05	$214.00
Purchase #4	$40.87	3.510%	$42.3045	$42.30	$42.30	$42.30
Purchase #5	$151.48	6.820%	$161.8109	$161.81	$161.80	$161.80
Purchase #6	$46.51	6.521%	$49.5429	$49.54	$49.55	$49.50
Purchase #7	$156.33	6.810%	$166.9761	$166.98	$167.00	$167.00
7 purchase totals =	$959.95		$1,019.5720	$1,019.57	$1,019.60	$1,019.50