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	$96.61	6.186%	$102.5863	$102.59	$102.60	$102.60
Purchase #2	$123.25	3.259%	$127.2667	$127.27	$127.25	$127.30
Purchase #3	$238.63	3.145%	$246.1349	$246.13	$246.15	$246.10
Purchase #4	$17.54	5.399%	$18.487	$18.49	$18.50	$18.50
Purchase #5	$47.80	13.561%	$54.2822	$54.28	$54.30	$54.30
Purchase #6	$60.48	13.542%	$68.6702	$68.67	$68.65	$68.70
Purchase #7	$119.96	6.528%	$127.791	$127.79	$127.80	$127.80
7 purchase totals =	$704.27		$745.2183	$745.22	$745.25	$745.30