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	$117.55	7.732%	$126.639	$126.64	$126.65	$126.60
Purchase #2	$120.92	13.502%	$137.2466	$137.25	$137.25	$137.20
Purchase #3	$77.76	5.583%	$82.1013	$82.10	$82.10	$82.10
Purchase #4	$106.30	12.297%	$119.3717	$119.37	$119.35	$119.40
Purchase #5	$102.89	6.543%	$109.6221	$109.62	$109.60	$109.60
Purchase #6	$54.66	13.581%	$62.0834	$62.08	$62.10	$62.10
Purchase #7	$166.30	11.105%	$184.7676	$184.77	$184.75	$184.80
7 purchase totals =	$746.38		$821.8317	$821.83	$821.80	$821.80