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	$84.71	7.211%	$90.8184	$90.82	$90.80	$90.80
Purchase #2	$187.96	6.404%	$199.997	$200.00	$200.00	$200.00
Purchase #3	$152.67	4.479%	$159.5081	$159.51	$159.50	$159.50
Purchase #4	$103.83	6.844%	$110.9361	$110.94	$110.95	$110.90
Purchase #5	$85.61	4.612%	$89.5583	$89.56	$89.55	$89.60
Purchase #6	$181.52	5.153%	$190.8737	$190.87	$190.85	$190.90
Purchase #7	$49.83	10.122%	$54.8738	$54.87	$54.85	$54.90
7 purchase totals =	$846.13		$896.5654	$896.57	$896.50	$896.60