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	$63.51	10.852%	$70.4021	$70.40	$70.40	$70.40
Purchase #2	$31.28	3.162%	$32.2691	$32.27	$32.25	$32.30
Purchase #3	$19.85	12.873%	$22.4053	$22.41	$22.40	$22.40
Purchase #4	$35.75	9.199%	$39.0386	$39.04	$39.05	$39.00
Purchase #5	$213.54	4.497%	$223.1429	$223.14	$223.15	$223.10
Purchase #6	$59.73	11.467%	$66.5792	$66.58	$66.60	$66.60
Purchase #7	$211.37	5.404%	$222.7924	$222.79	$222.80	$222.80
7 purchase totals =	$635.03		$676.6296	$676.63	$676.65	$676.60