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	$209.39	8.451%	$227.0855	$227.09	$227.10	$227.10
Purchase #2	$228.47	9.721%	$250.6796	$250.68	$250.70	$250.70
Purchase #3	$51.57	7.249%	$55.3083	$55.31	$55.30	$55.30
Purchase #4	$85.69	12.179%	$96.1262	$96.13	$96.15	$96.10
Purchase #5	$178.54	5.541%	$188.4329	$188.43	$188.45	$188.40
Purchase #6	$121.81	4.401%	$127.1709	$127.17	$127.15	$127.20
Purchase #7	$179.38	4.578%	$187.592	$187.59	$187.60	$187.60
7 purchase totals =	$1,054.85		$1,132.3954	$1,132.40	$1,132.45	$1,132.40