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	$171.40	3.127%	$176.7597	$176.76	$176.75	$176.80
Purchase #2	$39.70	12.517%	$44.6692	$44.67	$44.65	$44.70
Purchase #3	$198.33	4.793%	$207.836	$207.84	$207.85	$207.80
Purchase #4	$231.53	3.169%	$238.8672	$238.87	$238.85	$238.90
Purchase #5	$81.69	5.402%	$86.1029	$86.10	$86.10	$86.10
Purchase #6	$199.57	11.387%	$222.295	$222.30	$222.30	$222.30
Purchase #7	$37.61	10.570%	$41.5854	$41.59	$41.60	$41.60
7 purchase totals =	$959.83		$1,018.1154	$1,018.13	$1,018.10	$1,018.20