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	$216.39	5.671%	$228.6615	$228.66	$228.65	$228.70
Purchase #2	$19.28	10.236%	$21.2535	$21.25	$21.25	$21.30
Purchase #3	$140.28	11.262%	$156.0783	$156.08	$156.10	$156.10
Purchase #4	$96.49	11.187%	$107.2843	$107.28	$107.30	$107.30
Purchase #5	$201.94	11.661%	$225.4882	$225.49	$225.50	$225.50
Purchase #6	$123.65	6.567%	$131.7701	$131.77	$131.75	$131.80
Purchase #7	$163.27	13.329%	$185.0323	$185.03	$185.05	$185.00
7 purchase totals =	$961.30		$1,055.5682	$1,055.56	$1,055.60	$1,055.70