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	$198.42	7.152%	$212.611	$212.61	$212.60	$212.60
Purchase #2	$85.87	5.156%	$90.2975	$90.30	$90.30	$90.30
Purchase #3	$27.95	9.616%	$30.6377	$30.64	$30.65	$30.60
Purchase #4	$131.46	10.429%	$145.17	$145.17	$145.15	$145.20
Purchase #5	$99.52	10.660%	$110.1288	$110.13	$110.15	$110.10
Purchase #6	$99.82	12.730%	$112.5271	$112.53	$112.55	$112.50
Purchase #7	$231.49	12.451%	$260.3128	$260.31	$260.30	$260.30
7 purchase totals =	$874.53		$961.6849	$961.69	$961.70	$961.60