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	$184.29	6.530%	$196.3241	$196.32	$196.30	$196.30
Purchase #2	$133.52	7.453%	$143.4712	$143.47	$143.45	$143.50
Purchase #3	$43.72	8.705%	$47.5258	$47.53	$47.55	$47.50
Purchase #4	$42.28	3.555%	$43.7831	$43.78	$43.80	$43.80
Purchase #5	$236.31	7.433%	$253.8749	$253.87	$253.85	$253.90
Purchase #6	$174.28	3.773%	$180.8556	$180.86	$180.85	$180.90
Purchase #7	$201.83	5.532%	$212.9952	$213.00	$213.00	$213.00
7 purchase totals =	$1,016.23		$1,078.8299	$1,078.83	$1,078.80	$1,078.90