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	$53.81	9.362%	$58.8477	$58.85	$58.85	$58.80
Purchase #2	$119.79	10.594%	$132.4806	$132.48	$132.50	$132.50
Purchase #3	$39.87	7.359%	$42.804	$42.80	$42.80	$42.80
Purchase #4	$92.98	11.404%	$103.5834	$103.58	$103.60	$103.60
Purchase #5	$101.90	13.289%	$115.4415	$115.44	$115.45	$115.40
Purchase #6	$204.41	6.149%	$216.9792	$216.98	$217.00	$217.00
Purchase #7	$52.76	3.658%	$54.69	$54.69	$54.70	$54.70
7 purchase totals =	$665.52		$724.8264	$724.82	$724.90	$724.80