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	$212.84	7.238%	$228.2454	$228.25	$228.25	$228.20
Purchase #2	$54.33	4.230%	$56.6282	$56.63	$56.65	$56.60
Purchase #3	$214.33	9.732%	$235.1886	$235.19	$235.20	$235.20
Purchase #4	$111.71	7.374%	$119.9475	$119.95	$119.95	$119.90
Purchase #5	$143.62	9.113%	$156.7081	$156.71	$156.70	$156.70
Purchase #6	$112.38	13.326%	$127.3558	$127.36	$127.35	$127.40
Purchase #7	$87.38	13.158%	$98.8775	$98.88	$98.90	$98.90
7 purchase totals =	$936.59		$1,022.9511	$1,022.97	$1,023.00	$1,022.90