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	$163.91	13.352%	$185.7953	$185.80	$185.80	$185.80
Purchase #2	$13.39	13.220%	$15.1602	$15.16	$15.15	$15.20
Purchase #3	$239.93	8.220%	$259.6522	$259.65	$259.65	$259.70
Purchase #4	$174.83	9.169%	$190.8602	$190.86	$190.85	$190.90
Purchase #5	$226.50	6.392%	$240.9779	$240.98	$241.00	$241.00
Purchase #6	$103.40	7.418%	$111.0702	$111.07	$111.05	$111.10
Purchase #7	$11.53	12.445%	$12.9649	$12.96	$12.95	$13.00
7 purchase totals =	$933.49		$1,016.4809	$1,016.48	$1,016.45	$1,016.70