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	$114.48	7.169%	$122.6871	$122.69	$122.70	$122.70
Purchase #2	$51.39	6.580%	$54.7715	$54.77	$54.75	$54.80
Purchase #3	$102.94	8.657%	$111.8515	$111.85	$111.85	$111.90
Purchase #4	$62.43	8.621%	$67.8121	$67.81	$67.80	$67.80
Purchase #5	$103.96	5.215%	$109.3815	$109.38	$109.40	$109.40
Purchase #6	$204.34	10.397%	$225.5852	$225.59	$225.60	$225.60
Purchase #7	$226.27	10.852%	$250.8248	$250.82	$250.80	$250.80
7 purchase totals =	$865.81		$942.9137	$942.91	$942.90	$943.00