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	$54.71	6.585%	$58.3127	$58.31	$58.30	$58.30
Purchase #2	$185.36	13.624%	$210.6134	$210.61	$210.60	$210.60
Purchase #3	$158.61	5.730%	$167.6984	$167.70	$167.70	$167.70
Purchase #4	$82.50	4.756%	$86.4237	$86.42	$86.40	$86.40
Purchase #5	$136.97	12.187%	$153.6625	$153.66	$153.65	$153.70
Purchase #6	$90.85	10.233%	$100.1467	$100.15	$100.15	$100.10
Purchase #7	$223.72	9.838%	$245.7296	$245.73	$245.75	$245.70
7 purchase totals =	$932.72		$1,022.5870	$1,022.58	$1,022.55	$1,022.50