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	$184.53	4.540%	$192.9077	$192.91	$192.90	$192.90
Purchase #2	$234.41	11.223%	$260.7178	$260.72	$260.70	$260.70
Purchase #3	$85.83	7.853%	$92.5702	$92.57	$92.55	$92.60
Purchase #4	$143.34	10.604%	$158.5398	$158.54	$158.55	$158.50
Purchase #5	$77.70	5.238%	$81.7699	$81.77	$81.75	$81.80
Purchase #6	$94.33	11.722%	$105.3874	$105.39	$105.40	$105.40
Purchase #7	$103.42	10.638%	$114.4218	$114.42	$114.40	$114.40
7 purchase totals =	$923.56		$1,006.3146	$1,006.32	$1,006.25	$1,006.30