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	$173.96	7.522%	$187.0453	$187.05	$187.05	$187.00
Purchase #2	$50.64	11.817%	$56.6241	$56.62	$56.60	$56.60
Purchase #3	$203.28	4.412%	$212.2487	$212.25	$212.25	$212.20
Purchase #4	$204.35	11.812%	$228.4878	$228.49	$228.50	$228.50
Purchase #5	$82.56	8.290%	$89.4042	$89.40	$89.40	$89.40
Purchase #6	$59.76	10.585%	$66.0856	$66.09	$66.10	$66.10
Purchase #7	$167.67	4.203%	$174.7172	$174.72	$174.70	$174.70
7 purchase totals =	$942.22		$1,014.6129	$1,014.62	$1,014.60	$1,014.50