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	$228.28	6.599%	$243.3442	$243.34	$243.35	$243.30
Purchase #2	$238.93	5.272%	$251.5264	$251.53	$251.55	$251.50
Purchase #3	$63.71	3.284%	$65.8022	$65.80	$65.80	$65.80
Purchase #4	$127.50	9.405%	$139.4914	$139.49	$139.50	$139.50
Purchase #5	$73.90	5.759%	$78.1559	$78.16	$78.15	$78.20
Purchase #6	$114.98	9.856%	$126.3124	$126.31	$126.30	$126.30
Purchase #7	$144.35	9.834%	$158.5454	$158.55	$158.55	$158.50
7 purchase totals =	$991.65		$1,063.1779	$1,063.18	$1,063.20	$1,063.10