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	$177.25	4.443%	$185.1252	$185.13	$185.15	$185.10
Purchase #2	$52.59	10.221%	$57.9652	$57.97	$57.95	$58.00
Purchase #3	$163.49	5.670%	$172.7599	$172.76	$172.75	$172.80
Purchase #4	$73.69	9.616%	$80.776	$80.78	$80.80	$80.80
Purchase #5	$157.52	4.693%	$164.9124	$164.91	$164.90	$164.90
Purchase #6	$161.97	8.128%	$175.1349	$175.13	$175.15	$175.10
Purchase #7	$233.26	6.845%	$249.2266	$249.23	$249.25	$249.20
7 purchase totals =	$1,019.77		$1,085.9002	$1,085.91	$1,085.95	$1,085.90