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	$172.39	3.441%	$178.3219	$178.32	$178.30	$178.30
Purchase #2	$107.64	3.444%	$111.3471	$111.35	$111.35	$111.30
Purchase #3	$37.98	12.755%	$42.8243	$42.82	$42.80	$42.80
Purchase #4	$14.89	11.622%	$16.6205	$16.62	$16.60	$16.60
Purchase #5	$223.52	4.566%	$233.7259	$233.73	$233.75	$233.70
Purchase #6	$142.88	13.425%	$162.0616	$162.06	$162.05	$162.10
Purchase #7	$64.51	3.702%	$66.8982	$66.90	$66.90	$66.90
7 purchase totals =	$763.81		$811.7995	$811.80	$811.75	$811.70