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	$37.66	3.102%	$38.8282	$38.83	$38.85	$38.80
Purchase #2	$246.68	6.420%	$262.5169	$262.52	$262.50	$262.50
Purchase #3	$49.92	6.860%	$53.3445	$53.34	$53.35	$53.30
Purchase #4	$11.33	10.562%	$12.5267	$12.53	$12.55	$12.50
Purchase #5	$85.74	5.263%	$90.2525	$90.25	$90.25	$90.30
Purchase #6	$212.27	7.164%	$227.477	$227.48	$227.50	$227.50
Purchase #7	$9.27	9.652%	$10.1647	$10.16	$10.15	$10.20
7 purchase totals =	$652.87		$695.1105	$695.11	$695.15	$695.10