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	$156.44	7.814%	$168.6642	$168.66	$168.65	$168.70
Purchase #2	$211.39	12.656%	$238.1435	$238.14	$238.15	$238.10
Purchase #3	$149.71	3.346%	$154.7193	$154.72	$154.70	$154.70
Purchase #4	$222.90	3.866%	$231.5173	$231.52	$231.50	$231.50
Purchase #5	$62.83	4.309%	$65.5373	$65.54	$65.55	$65.50
Purchase #6	$21.98	9.555%	$24.0802	$24.08	$24.10	$24.10
Purchase #7	$159.79	11.693%	$178.4742	$178.47	$178.45	$178.50
7 purchase totals =	$985.04		$1,061.1360	$1,061.13	$1,061.10	$1,061.10