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	$68.33	5.453%	$72.056	$72.06	$72.05	$72.10
Purchase #2	$250.76	5.739%	$265.1511	$265.15	$265.15	$265.20
Purchase #3	$239.59	13.543%	$272.0377	$272.04	$272.05	$272.00
Purchase #4	$151.96	9.693%	$166.6895	$166.69	$166.70	$166.70
Purchase #5	$88.41	4.380%	$92.2824	$92.28	$92.30	$92.30
Purchase #6	$172.46	10.620%	$190.7753	$190.78	$190.80	$190.80
Purchase #7	$30.45	6.172%	$32.3294	$32.33	$32.35	$32.30
7 purchase totals =	$1,001.96		$1,091.3214	$1,091.33	$1,091.40	$1,091.40