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	$217.44	6.266%	$231.0648	$231.06	$231.05	$231.10
Purchase #2	$112.30	10.837%	$124.47	$124.47	$124.45	$124.50
Purchase #3	$154.56	11.293%	$172.0145	$172.01	$172.00	$172.00
Purchase #4	$55.72	4.571%	$58.267	$58.27	$58.25	$58.30
Purchase #5	$215.60	9.734%	$236.5865	$236.59	$236.60	$236.60
Purchase #6	$227.41	6.647%	$242.5259	$242.53	$242.55	$242.50
Purchase #7	$11.95	4.278%	$12.4612	$12.46	$12.45	$12.50
7 purchase totals =	$994.98		$1,077.3899	$1,077.39	$1,077.35	$1,077.50