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	$81.96	5.486%	$86.4563	$86.46	$86.45	$86.50
Purchase #2	$165.42	9.263%	$180.7429	$180.74	$180.75	$180.70
Purchase #3	$127.78	3.618%	$132.4031	$132.40	$132.40	$132.40
Purchase #4	$182.86	4.158%	$190.4633	$190.46	$190.45	$190.50
Purchase #5	$39.74	5.530%	$41.9376	$41.94	$41.95	$41.90
Purchase #6	$153.72	12.459%	$172.872	$172.87	$172.85	$172.90
Purchase #7	$210.41	11.428%	$234.4557	$234.46	$234.45	$234.50
7 purchase totals =	$961.89		$1,039.3309	$1,039.33	$1,039.30	$1,039.40