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	$209.37	11.752%	$233.9752	$233.98	$234.00	$234.00
Purchase #2	$108.92	13.291%	$123.3966	$123.40	$123.40	$123.40
Purchase #3	$139.43	5.610%	$147.252	$147.25	$147.25	$147.30
Purchase #4	$219.27	12.151%	$245.9135	$245.91	$245.90	$245.90
Purchase #5	$241.96	5.607%	$255.5267	$255.53	$255.55	$255.50
Purchase #6	$17.95	10.769%	$19.883	$19.88	$19.90	$19.90
Purchase #7	$209.90	10.318%	$231.5575	$231.56	$231.55	$231.60
7 purchase totals =	$1,146.80		$1,257.5045	$1,257.51	$1,257.55	$1,257.60