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	$98.87	12.161%	$110.8936	$110.89	$110.90	$110.90
Purchase #2	$205.50	8.711%	$223.4011	$223.40	$223.40	$223.40
Purchase #3	$37.38	6.710%	$39.8882	$39.89	$39.90	$39.90
Purchase #4	$29.26	11.705%	$32.6849	$32.68	$32.70	$32.70
Purchase #5	$134.60	12.217%	$151.0441	$151.04	$151.05	$151.00
Purchase #6	$13.97	5.432%	$14.7289	$14.73	$14.75	$14.70
Purchase #7	$98.88	12.566%	$111.3053	$111.31	$111.30	$111.30
7 purchase totals =	$618.46		$683.9461	$683.94	$684.00	$683.90