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	$49.94	3.274%	$51.575	$51.58	$51.60	$51.60
Purchase #2	$62.27	7.784%	$67.1171	$67.12	$67.10	$67.10
Purchase #3	$97.64	5.326%	$102.8403	$102.84	$102.85	$102.80
Purchase #4	$165.83	12.391%	$186.378	$186.38	$186.40	$186.40
Purchase #5	$89.75	13.492%	$101.8591	$101.86	$101.85	$101.90
Purchase #6	$216.87	11.299%	$241.3741	$241.37	$241.35	$241.40
Purchase #7	$147.61	6.230%	$156.8061	$156.81	$156.80	$156.80
7 purchase totals =	$829.91		$907.9497	$907.96	$907.95	$908.00