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	$112.91	5.339%	$118.9383	$118.94	$118.95	$118.90
Purchase #2	$91.78	4.600%	$96.0019	$96.00	$96.00	$96.00
Purchase #3	$85.26	3.233%	$88.0165	$88.02	$88.00	$88.00
Purchase #4	$101.85	9.116%	$111.1346	$111.13	$111.15	$111.10
Purchase #5	$76.81	4.307%	$80.1182	$80.12	$80.10	$80.10
Purchase #6	$107.94	4.492%	$112.7887	$112.79	$112.80	$112.80
Purchase #7	$72.36	8.311%	$78.3738	$78.37	$78.35	$78.40
7 purchase totals =	$648.91		$685.3720	$685.37	$685.35	$685.30