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	$105.57	5.512%	$111.389	$111.39	$111.40	$111.40
Purchase #2	$216.41	10.204%	$238.4925	$238.49	$238.50	$238.50
Purchase #3	$245.71	7.242%	$263.5043	$263.50	$263.50	$263.50
Purchase #4	$156.44	6.789%	$167.0607	$167.06	$167.05	$167.10
Purchase #5	$206.43	9.778%	$226.6147	$226.61	$226.60	$226.60
Purchase #6	$183.34	11.476%	$204.3801	$204.38	$204.40	$204.40
Purchase #7	$205.52	12.646%	$231.5101	$231.51	$231.50	$231.50
7 purchase totals =	$1,319.42		$1,442.9514	$1,442.94	$1,442.95	$1,443.00