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	$231.33	10.498%	$255.615	$255.62	$255.60	$255.60
Purchase #2	$20.55	6.436%	$21.8726	$21.87	$21.85	$21.90
Purchase #3	$45.73	9.281%	$49.9742	$49.97	$49.95	$50.00
Purchase #4	$226.87	7.474%	$243.8263	$243.83	$243.85	$243.80
Purchase #5	$64.43	3.747%	$66.8442	$66.84	$66.85	$66.80
Purchase #6	$179.82	5.675%	$190.0248	$190.02	$190.00	$190.00
Purchase #7	$222.87	10.635%	$246.5722	$246.57	$246.55	$246.60
7 purchase totals =	$991.60		$1,074.7293	$1,074.72	$1,074.65	$1,074.70