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	$130.40	8.700%	$141.7448	$141.74	$141.75	$141.70
Purchase #2	$110.51	3.682%	$114.579	$114.58	$114.60	$114.60
Purchase #3	$93.73	4.567%	$98.0106	$98.01	$98.00	$98.00
Purchase #4	$172.46	11.668%	$192.5826	$192.58	$192.60	$192.60
Purchase #5	$134.95	12.821%	$152.2519	$152.25	$152.25	$152.30
Purchase #6	$238.67	11.632%	$266.4321	$266.43	$266.45	$266.40
Purchase #7	$116.38	6.404%	$123.833	$123.83	$123.85	$123.80
7 purchase totals =	$997.10		$1,089.4340	$1,089.42	$1,089.50	$1,089.40