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	$208.37	6.291%	$221.4786	$221.48	$221.50	$221.50
Purchase #2	$89.52	11.681%	$99.9768	$99.98	$100.00	$100.00
Purchase #3	$9.54	9.582%	$10.4541	$10.45	$10.45	$10.50
Purchase #4	$105.29	9.723%	$115.5273	$115.53	$115.55	$115.50
Purchase #5	$148.69	6.285%	$158.0352	$158.04	$158.05	$158.00
Purchase #6	$224.61	11.267%	$249.9168	$249.92	$249.90	$249.90
Purchase #7	$174.61	8.820%	$190.0106	$190.01	$190.00	$190.00
7 purchase totals =	$960.63		$1,045.3994	$1,045.41	$1,045.45	$1,045.40