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	$42.32	6.295%	$44.984	$44.98	$45.00	$45.00
Purchase #2	$52.25	8.380%	$56.6286	$56.63	$56.65	$56.60
Purchase #3	$112.38	11.760%	$125.5959	$125.60	$125.60	$125.60
Purchase #4	$234.25	13.558%	$266.0096	$266.01	$266.00	$266.00
Purchase #5	$129.94	10.495%	$143.5772	$143.58	$143.60	$143.60
Purchase #6	$90.98	5.454%	$95.942	$95.94	$95.95	$95.90
Purchase #7	$250.74	11.738%	$280.1719	$280.17	$280.15	$280.20
7 purchase totals =	$912.86		$1,012.9092	$1,012.91	$1,012.95	$1,012.90