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	$171.86	13.356%	$194.8136	$194.81	$194.80	$194.80
Purchase #2	$236.60	11.385%	$263.5369	$263.54	$263.55	$263.50
Purchase #3	$50.76	5.170%	$53.3843	$53.38	$53.40	$53.40
Purchase #4	$196.26	7.812%	$211.5918	$211.59	$211.60	$211.60
Purchase #5	$166.40	5.810%	$176.0678	$176.07	$176.05	$176.10
Purchase #6	$107.60	6.790%	$114.906	$114.91	$114.90	$114.90
Purchase #7	$172.29	5.710%	$182.1278	$182.13	$182.15	$182.10
7 purchase totals =	$1,101.77		$1,196.4282	$1,196.43	$1,196.45	$1,196.40