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	$101.28	6.165%	$107.5239	$107.52	$107.50	$107.50
Purchase #2	$66.52	9.190%	$72.6332	$72.63	$72.65	$72.60
Purchase #3	$221.88	10.334%	$244.8091	$244.81	$244.80	$244.80
Purchase #4	$14.27	4.129%	$14.8592	$14.86	$14.85	$14.90
Purchase #5	$241.96	5.580%	$255.4614	$255.46	$255.45	$255.50
Purchase #6	$131.44	8.368%	$142.4389	$142.44	$142.45	$142.40
Purchase #7	$102.60	7.157%	$109.9431	$109.94	$109.95	$109.90
7 purchase totals =	$879.95		$947.6688	$947.66	$947.65	$947.60