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	$111.65	9.546%	$122.3081	$122.31	$122.30	$122.30
Purchase #2	$173.46	6.153%	$184.133	$184.13	$184.15	$184.10
Purchase #3	$96.85	7.653%	$104.2619	$104.26	$104.25	$104.30
Purchase #4	$198.33	13.855%	$225.8086	$225.81	$225.80	$225.80
Purchase #5	$243.77	13.617%	$276.9642	$276.96	$276.95	$277.00
Purchase #6	$56.41	5.429%	$59.4725	$59.47	$59.45	$59.50
Purchase #7	$39.50	10.690%	$43.7226	$43.72	$43.70	$43.70
7 purchase totals =	$919.97		$1,016.6709	$1,016.66	$1,016.60	$1,016.70