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	$84.48	9.540%	$92.5394	$92.54	$92.55	$92.50
Purchase #2	$238.41	7.286%	$255.7806	$255.78	$255.80	$255.80
Purchase #3	$104.71	13.278%	$118.6134	$118.61	$118.60	$118.60
Purchase #4	$49.80	8.771%	$54.168	$54.17	$54.15	$54.20
Purchase #5	$27.59	8.351%	$29.894	$29.89	$29.90	$29.90
Purchase #6	$55.30	9.118%	$60.3423	$60.34	$60.35	$60.30
Purchase #7	$167.71	4.574%	$175.3811	$175.38	$175.40	$175.40
7 purchase totals =	$728.00		$786.7188	$786.71	$786.75	$786.70