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	$236.86	11.718%	$264.6153	$264.62	$264.60	$264.60
Purchase #2	$90.71	13.490%	$102.9468	$102.95	$102.95	$102.90
Purchase #3	$231.42	10.264%	$255.1729	$255.17	$255.15	$255.20
Purchase #4	$13.51	11.405%	$15.0508	$15.05	$15.05	$15.10
Purchase #5	$100.88	8.750%	$109.707	$109.71	$109.70	$109.70
Purchase #6	$195.83	4.452%	$204.5484	$204.55	$204.55	$204.50
Purchase #7	$106.33	8.704%	$115.585	$115.59	$115.60	$115.60
7 purchase totals =	$975.54		$1,067.6262	$1,067.64	$1,067.60	$1,067.60