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	$115.39	10.747%	$127.791	$127.79	$127.80	$127.80
Purchase #2	$115.79	13.366%	$131.2665	$131.27	$131.25	$131.30
Purchase #3	$25.57	9.288%	$27.9449	$27.94	$27.95	$27.90
Purchase #4	$49.37	8.578%	$53.605	$53.61	$53.60	$53.60
Purchase #5	$110.70	8.828%	$120.4726	$120.47	$120.45	$120.50
Purchase #6	$107.70	8.530%	$116.8868	$116.89	$116.90	$116.90
Purchase #7	$192.91	6.819%	$206.0645	$206.06	$206.05	$206.10
7 purchase totals =	$717.43		$784.0313	$784.03	$784.00	$784.10