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	$244.75	5.558%	$258.3532	$258.35	$258.35	$258.40
Purchase #2	$162.60	6.857%	$173.7495	$173.75	$173.75	$173.70
Purchase #3	$77.57	3.565%	$80.3354	$80.34	$80.35	$80.30
Purchase #4	$123.88	13.451%	$140.5431	$140.54	$140.55	$140.50
Purchase #5	$71.87	9.616%	$78.781	$78.78	$78.80	$78.80
Purchase #6	$159.92	4.730%	$167.4842	$167.48	$167.50	$167.50
Purchase #7	$230.58	6.321%	$245.155	$245.16	$245.15	$245.20
7 purchase totals =	$1,071.17		$1,144.4014	$1,144.40	$1,144.45	$1,144.40