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	$182.46	9.279%	$199.3905	$199.39	$199.40	$199.40
Purchase #2	$64.32	12.661%	$72.4636	$72.46	$72.45	$72.50
Purchase #3	$88.88	12.495%	$99.9856	$99.99	$100.00	$100.00
Purchase #4	$246.69	4.541%	$257.8922	$257.89	$257.90	$257.90
Purchase #5	$23.38	3.117%	$24.1088	$24.11	$24.10	$24.10
Purchase #6	$151.59	6.433%	$161.3418	$161.34	$161.35	$161.30
Purchase #7	$166.71	11.365%	$185.6566	$185.66	$185.65	$185.70
7 purchase totals =	$924.03		$1,000.8391	$1,000.84	$1,000.85	$1,000.90