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	$171.52	7.851%	$184.986	$184.99	$185.00	$185.00
Purchase #2	$38.48	6.163%	$40.8515	$40.85	$40.85	$40.90
Purchase #3	$242.76	10.784%	$268.9392	$268.94	$268.95	$268.90
Purchase #4	$97.53	8.627%	$105.9439	$105.94	$105.95	$105.90
Purchase #5	$176.75	7.793%	$190.5241	$190.52	$190.50	$190.50
Purchase #6	$145.70	13.236%	$164.9849	$164.98	$165.00	$165.00
Purchase #7	$118.37	9.373%	$129.4648	$129.46	$129.45	$129.50
7 purchase totals =	$991.11		$1,085.6944	$1,085.68	$1,085.70	$1,085.70