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	$43.71	7.182%	$46.8493	$46.85	$46.85	$46.80
Purchase #2	$182.86	9.568%	$200.356	$200.36	$200.35	$200.40
Purchase #3	$216.32	8.701%	$235.142	$235.14	$235.15	$235.10
Purchase #4	$249.47	8.461%	$270.5777	$270.58	$270.60	$270.60
Purchase #5	$96.41	7.324%	$103.4711	$103.47	$103.45	$103.50
Purchase #6	$116.34	10.620%	$128.6953	$128.70	$128.70	$128.70
Purchase #7	$119.97	9.526%	$131.3983	$131.40	$131.40	$131.40
7 purchase totals =	$1,025.08		$1,116.4897	$1,116.50	$1,116.50	$1,116.50