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	$183.82	13.715%	$209.0309	$209.03	$209.05	$209.00
Purchase #2	$70.62	13.147%	$79.9044	$79.90	$79.90	$79.90
Purchase #3	$99.70	4.835%	$104.5205	$104.52	$104.50	$104.50
Purchase #4	$11.27	11.817%	$12.6018	$12.60	$12.60	$12.60
Purchase #5	$49.76	7.439%	$53.4616	$53.46	$53.45	$53.50
Purchase #6	$191.91	10.392%	$211.8533	$211.85	$211.85	$211.90
Purchase #7	$154.84	7.268%	$166.0938	$166.09	$166.10	$166.10
7 purchase totals =	$761.92		$837.4663	$837.45	$837.45	$837.50