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	$66.73	8.160%	$72.1752	$72.18	$72.20	$72.20
Purchase #2	$190.43	7.839%	$205.3578	$205.36	$205.35	$205.40
Purchase #3	$182.83	4.729%	$191.476	$191.48	$191.50	$191.50
Purchase #4	$124.35	8.147%	$134.4808	$134.48	$134.50	$134.50
Purchase #5	$57.65	8.192%	$62.3727	$62.37	$62.35	$62.40
Purchase #6	$65.32	3.178%	$67.3959	$67.40	$67.40	$67.40
Purchase #7	$126.52	8.498%	$137.2717	$137.27	$137.25	$137.30
7 purchase totals =	$813.83		$870.5301	$870.54	$870.55	$870.70