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	$184.53	8.382%	$199.9973	$200.00	$200.00	$200.00
Purchase #2	$94.34	6.292%	$100.2759	$100.28	$100.30	$100.30
Purchase #3	$52.69	3.773%	$54.678	$54.68	$54.70	$54.70
Purchase #4	$85.59	6.159%	$90.8615	$90.86	$90.85	$90.90
Purchase #5	$33.61	13.315%	$38.0852	$38.09	$38.10	$38.10
Purchase #6	$20.75	8.675%	$22.5501	$22.55	$22.55	$22.60
Purchase #7	$42.66	10.487%	$47.1338	$47.13	$47.15	$47.10
7 purchase totals =	$514.17		$553.5818	$553.59	$553.65	$553.70