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	$81.26	4.521%	$84.9338	$84.93	$84.95	$84.90
Purchase #2	$155.86	8.274%	$168.7559	$168.76	$168.75	$168.80
Purchase #3	$108.35	10.534%	$119.7636	$119.76	$119.75	$119.80
Purchase #4	$131.60	12.244%	$147.7131	$147.71	$147.70	$147.70
Purchase #5	$49.64	7.422%	$53.3243	$53.32	$53.30	$53.30
Purchase #6	$42.60	6.151%	$45.2203	$45.22	$45.20	$45.20
Purchase #7	$85.27	5.182%	$89.6887	$89.69	$89.70	$89.70
7 purchase totals =	$654.58		$709.3997	$709.39	$709.35	$709.40