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	$223.69	9.696%	$245.379	$245.38	$245.40	$245.40
Purchase #2	$104.95	6.770%	$112.0551	$112.06	$112.05	$112.10
Purchase #3	$176.72	6.672%	$188.5108	$188.51	$188.50	$188.50
Purchase #4	$186.73	3.279%	$192.8529	$192.85	$192.85	$192.90
Purchase #5	$111.47	10.487%	$123.1599	$123.16	$123.15	$123.20
Purchase #6	$106.72	7.649%	$114.883	$114.88	$114.90	$114.90
Purchase #7	$204.52	13.406%	$231.938	$231.94	$231.95	$231.90
7 purchase totals =	$1,114.80		$1,208.7787	$1,208.78	$1,208.80	$1,208.90