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	$130.37	11.198%	$144.9688	$144.97	$144.95	$145.00
Purchase #2	$50.35	9.198%	$54.9812	$54.98	$55.00	$55.00
Purchase #3	$158.72	9.189%	$173.3048	$173.30	$173.30	$173.30
Purchase #4	$231.31	7.109%	$247.7538	$247.75	$247.75	$247.80
Purchase #5	$98.82	6.634%	$105.3757	$105.38	$105.40	$105.40
Purchase #6	$81.74	9.598%	$89.5854	$89.59	$89.60	$89.60
Purchase #7	$103.92	6.751%	$110.9356	$110.94	$110.95	$110.90
7 purchase totals =	$855.23		$926.9053	$926.91	$926.95	$927.00