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	$66.44	3.231%	$68.5867	$68.59	$68.60	$68.60
Purchase #2	$85.94	4.206%	$89.5546	$89.55	$89.55	$89.60
Purchase #3	$39.62	7.756%	$42.6929	$42.69	$42.70	$42.70
Purchase #4	$96.65	4.629%	$101.1239	$101.12	$101.10	$101.10
Purchase #5	$174.72	7.246%	$187.3802	$187.38	$187.40	$187.40
Purchase #6	$46.50	5.739%	$49.1686	$49.17	$49.15	$49.20
Purchase #7	$222.27	10.198%	$244.9371	$244.94	$244.95	$244.90
7 purchase totals =	$732.14		$783.4440	$783.44	$783.45	$783.50