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	$218.94	10.554%	$242.0469	$242.05	$242.05	$242.00
Purchase #2	$166.88	5.431%	$175.9433	$175.94	$175.95	$175.90
Purchase #3	$142.64	6.172%	$151.4437	$151.44	$151.45	$151.40
Purchase #4	$37.77	9.629%	$41.4069	$41.41	$41.40	$41.40
Purchase #5	$214.52	6.174%	$227.7645	$227.76	$227.75	$227.80
Purchase #6	$111.27	3.629%	$115.308	$115.31	$115.30	$115.30
Purchase #7	$172.31	10.278%	$190.02	$190.02	$190.00	$190.00
7 purchase totals =	$1,064.33		$1,143.9333	$1,143.93	$1,143.90	$1,143.80