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	$101.67	12.549%	$114.4286	$114.43	$114.45	$114.40
Purchase #2	$249.83	8.304%	$270.5759	$270.58	$270.60	$270.60
Purchase #3	$174.80	9.621%	$191.6175	$191.62	$191.60	$191.60
Purchase #4	$43.87	4.466%	$45.8292	$45.83	$45.85	$45.80
Purchase #5	$210.89	13.246%	$238.8245	$238.82	$238.80	$238.80
Purchase #6	$192.97	3.817%	$200.3357	$200.34	$200.35	$200.30
Purchase #7	$167.75	3.179%	$173.0828	$173.08	$173.10	$173.10
7 purchase totals =	$1,141.78		$1,234.6942	$1,234.70	$1,234.75	$1,234.60