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	$230.77	6.586%	$245.9685	$245.97	$245.95	$246.00
Purchase #2	$195.45	11.168%	$217.2779	$217.28	$217.30	$217.30
Purchase #3	$128.46	8.234%	$139.0374	$139.04	$139.05	$139.00
Purchase #4	$167.37	10.728%	$185.3255	$185.33	$185.35	$185.30
Purchase #5	$139.60	4.508%	$145.8932	$145.89	$145.90	$145.90
Purchase #6	$98.41	5.570%	$103.8914	$103.89	$103.90	$103.90
Purchase #7	$10.35	12.314%	$11.6245	$11.62	$11.60	$11.60
7 purchase totals =	$970.41		$1,049.0184	$1,049.02	$1,049.05	$1,049.00