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	$227.54	11.530%	$253.7754	$253.78	$253.80	$253.80
Purchase #2	$73.62	7.715%	$79.2998	$79.30	$79.30	$79.30
Purchase #3	$231.70	8.508%	$251.413	$251.41	$251.40	$251.40
Purchase #4	$75.95	3.820%	$78.8513	$78.85	$78.85	$78.90
Purchase #5	$151.61	9.867%	$166.5694	$166.57	$166.55	$166.60
Purchase #6	$211.58	5.206%	$222.5949	$222.59	$222.60	$222.60
Purchase #7	$41.35	13.465%	$46.9178	$46.92	$46.90	$46.90
7 purchase totals =	$1,013.35		$1,099.4216	$1,099.42	$1,099.40	$1,099.50