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	$126.71	6.144%	$134.4951	$134.50	$134.50	$134.50
Purchase #2	$107.25	11.871%	$119.9816	$119.98	$120.00	$120.00
Purchase #3	$82.66	10.241%	$91.1252	$91.13	$91.15	$91.10
Purchase #4	$194.89	3.394%	$201.5046	$201.50	$201.50	$201.50
Purchase #5	$96.34	4.664%	$100.8333	$100.83	$100.85	$100.80
Purchase #6	$228.40	11.788%	$255.3238	$255.32	$255.30	$255.30
Purchase #7	$233.71	12.281%	$262.4119	$262.41	$262.40	$262.40
7 purchase totals =	$1,069.96		$1,165.6755	$1,165.67	$1,165.70	$1,165.60