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	$95.89	4.345%	$100.0564	$100.06	$100.05	$100.10
Purchase #2	$33.57	3.779%	$34.8386	$34.84	$34.85	$34.80
Purchase #3	$160.71	4.373%	$167.7378	$167.74	$167.75	$167.70
Purchase #4	$135.50	9.634%	$148.5541	$148.55	$148.55	$148.60
Purchase #5	$41.64	4.672%	$43.5854	$43.59	$43.60	$43.60
Purchase #6	$86.67	5.688%	$91.5998	$91.60	$91.60	$91.60
Purchase #7	$177.31	5.223%	$186.5709	$186.57	$186.55	$186.60
7 purchase totals =	$731.29		$772.9430	$772.95	$772.95	$773.00