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	$118.52	7.726%	$127.6769	$127.68	$127.70	$127.70
Purchase #2	$148.30	12.296%	$166.535	$166.54	$166.55	$166.50
Purchase #3	$132.77	8.574%	$144.1537	$144.15	$144.15	$144.20
Purchase #4	$109.72	10.185%	$120.895	$120.90	$120.90	$120.90
Purchase #5	$122.33	12.481%	$137.598	$137.60	$137.60	$137.60
Purchase #6	$110.63	7.208%	$118.6042	$118.60	$118.60	$118.60
Purchase #7	$122.26	5.179%	$128.5918	$128.59	$128.60	$128.60
7 purchase totals =	$864.53		$944.0546	$944.06	$944.10	$944.10