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	$143.82	8.715%	$156.3539	$156.35	$156.35	$156.40
Purchase #2	$87.62	3.700%	$90.8619	$90.86	$90.85	$90.90
Purchase #3	$104.88	5.274%	$110.4114	$110.41	$110.40	$110.40
Purchase #4	$57.49	9.693%	$63.0625	$63.06	$63.05	$63.10
Purchase #5	$125.65	12.701%	$141.6088	$141.61	$141.60	$141.60
Purchase #6	$207.65	7.455%	$223.1303	$223.13	$223.15	$223.10
Purchase #7	$103.28	10.620%	$114.2483	$114.25	$114.25	$114.20
7 purchase totals =	$830.39		$899.6771	$899.67	$899.65	$899.70