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	$180.67	10.872%	$200.3124	$200.31	$200.30	$200.30
Purchase #2	$14.38	4.756%	$15.0639	$15.06	$15.05	$15.10
Purchase #3	$28.35	9.640%	$31.0829	$31.08	$31.10	$31.10
Purchase #4	$39.76	3.257%	$41.055	$41.06	$41.05	$41.10
Purchase #5	$59.52	13.730%	$67.6921	$67.69	$67.70	$67.70
Purchase #6	$223.61	12.665%	$251.9302	$251.93	$251.95	$251.90
Purchase #7	$104.61	5.393%	$110.2516	$110.25	$110.25	$110.30
7 purchase totals =	$650.90		$717.3881	$717.38	$717.40	$717.50