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	$123.70	3.317%	$127.8031	$127.80	$127.80	$127.80
Purchase #2	$247.47	5.122%	$260.1454	$260.15	$260.15	$260.10
Purchase #3	$224.40	4.628%	$234.7852	$234.79	$234.80	$234.80
Purchase #4	$147.63	10.105%	$162.548	$162.55	$162.55	$162.50
Purchase #5	$49.66	11.663%	$55.4518	$55.45	$55.45	$55.50
Purchase #6	$30.60	4.793%	$32.0667	$32.07	$32.05	$32.10
Purchase #7	$172.65	13.597%	$196.1252	$196.13	$196.15	$196.10
7 purchase totals =	$996.11		$1,068.9254	$1,068.94	$1,068.95	$1,068.90