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	$163.27	12.583%	$183.8143	$183.81	$183.80	$183.80
Purchase #2	$90.74	8.581%	$98.5264	$98.53	$98.55	$98.50
Purchase #3	$10.99	8.187%	$11.8898	$11.89	$11.90	$11.90
Purchase #4	$204.98	8.344%	$222.0835	$222.08	$222.10	$222.10
Purchase #5	$144.91	4.102%	$150.8542	$150.85	$150.85	$150.90
Purchase #6	$156.75	9.732%	$172.0049	$172.00	$172.00	$172.00
Purchase #7	$190.84	13.835%	$217.2427	$217.24	$217.25	$217.20
7 purchase totals =	$962.48		$1,056.4158	$1,056.40	$1,056.45	$1,056.40