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	$49.42	9.410%	$54.0704	$54.07	$54.05	$54.10
Purchase #2	$67.83	5.783%	$71.7526	$71.75	$71.75	$71.80
Purchase #3	$95.50	4.651%	$99.9417	$99.94	$99.95	$99.90
Purchase #4	$104.56	6.315%	$111.163	$111.16	$111.15	$111.20
Purchase #5	$158.46	12.490%	$178.2517	$178.25	$178.25	$178.30
Purchase #6	$249.63	13.868%	$284.2487	$284.25	$284.25	$284.20
Purchase #7	$121.97	5.417%	$128.5771	$128.58	$128.60	$128.60
7 purchase totals =	$847.37		$928.0052	$928.00	$928.00	$928.10