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	$177.51	13.138%	$200.8313	$200.83	$200.85	$200.80
Purchase #2	$131.71	8.564%	$142.9896	$142.99	$143.00	$143.00
Purchase #3	$223.68	11.572%	$249.5642	$249.56	$249.55	$249.60
Purchase #4	$49.79	8.272%	$53.9086	$53.91	$53.90	$53.90
Purchase #5	$164.38	4.676%	$172.0664	$172.07	$172.05	$172.10
Purchase #6	$219.71	11.684%	$245.3809	$245.38	$245.40	$245.40
Purchase #7	$52.67	3.868%	$54.7073	$54.71	$54.70	$54.70
7 purchase totals =	$1,019.45		$1,119.4483	$1,119.45	$1,119.45	$1,119.50