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	$111.28	10.817%	$123.3172	$123.32	$123.30	$123.30
Purchase #2	$24.70	3.254%	$25.5037	$25.50	$25.50	$25.50
Purchase #3	$81.35	6.292%	$86.4685	$86.47	$86.45	$86.50
Purchase #4	$237.94	4.675%	$249.0637	$249.06	$249.05	$249.10
Purchase #5	$171.51	13.610%	$194.8525	$194.85	$194.85	$194.90
Purchase #6	$67.64	3.602%	$70.0764	$70.08	$70.10	$70.10
Purchase #7	$147.39	10.462%	$162.8099	$162.81	$162.80	$162.80
7 purchase totals =	$841.81		$912.0919	$912.09	$912.05	$912.20