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	$100.44	3.275%	$103.7294	$103.73	$103.75	$103.70
Purchase #2	$114.93	4.487%	$120.0869	$120.09	$120.10	$120.10
Purchase #3	$42.25	8.861%	$45.9938	$45.99	$46.00	$46.00
Purchase #4	$196.45	13.144%	$222.2714	$222.27	$222.25	$222.30
Purchase #5	$179.94	11.188%	$200.0717	$200.07	$200.05	$200.10
Purchase #6	$61.78	6.824%	$65.9959	$66.00	$66.00	$66.00
Purchase #7	$224.66	13.857%	$255.7911	$255.79	$255.80	$255.80
7 purchase totals =	$920.45		$1,013.9402	$1,013.94	$1,013.95	$1,014.00