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	$42.44	7.409%	$45.5844	$45.58	$45.60	$45.60
Purchase #2	$167.81	3.858%	$174.2841	$174.28	$174.30	$174.30
Purchase #3	$205.70	7.236%	$220.5845	$220.58	$220.60	$220.60
Purchase #4	$239.33	8.383%	$259.393	$259.39	$259.40	$259.40
Purchase #5	$108.82	3.106%	$112.1999	$112.20	$112.20	$112.20
Purchase #6	$217.87	10.588%	$240.9381	$240.94	$240.95	$240.90
Purchase #7	$37.38	3.734%	$38.7758	$38.78	$38.80	$38.80
7 purchase totals =	$1,019.35		$1,091.7598	$1,091.75	$1,091.85	$1,091.80