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	$127.56	13.599%	$144.9069	$144.91	$144.90	$144.90
Purchase #2	$219.38	6.429%	$233.4839	$233.48	$233.50	$233.50
Purchase #3	$193.79	13.711%	$220.3605	$220.36	$220.35	$220.40
Purchase #4	$102.51	9.441%	$112.188	$112.19	$112.20	$112.20
Purchase #5	$151.34	3.563%	$156.7322	$156.73	$156.75	$156.70
Purchase #6	$71.80	9.803%	$78.8386	$78.84	$78.85	$78.80
Purchase #7	$132.40	4.724%	$138.6546	$138.65	$138.65	$138.70
7 purchase totals =	$998.78		$1,085.1647	$1,085.16	$1,085.20	$1,085.20