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	$64.29	12.105%	$72.0723	$72.07	$72.05	$72.10
Purchase #2	$59.74	13.455%	$67.778	$67.78	$67.80	$67.80
Purchase #3	$52.77	7.758%	$56.8639	$56.86	$56.85	$56.90
Purchase #4	$155.31	7.386%	$166.7812	$166.78	$166.80	$166.80
Purchase #5	$127.70	5.428%	$134.6316	$134.63	$134.65	$134.60
Purchase #6	$174.25	4.237%	$181.633	$181.63	$181.65	$181.60
Purchase #7	$188.44	5.119%	$198.0862	$198.09	$198.10	$198.10
7 purchase totals =	$822.50		$877.8462	$877.84	$877.90	$877.90