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	$52.89	6.158%	$56.147	$56.15	$56.15	$56.10
Purchase #2	$241.42	10.297%	$266.279	$266.28	$266.30	$266.30
Purchase #3	$196.31	7.179%	$210.4031	$210.40	$210.40	$210.40
Purchase #4	$175.61	9.639%	$192.537	$192.54	$192.55	$192.50
Purchase #5	$211.70	7.172%	$226.8831	$226.88	$226.90	$226.90
Purchase #6	$173.30	10.780%	$191.9817	$191.98	$192.00	$192.00
Purchase #7	$91.48	13.124%	$103.4858	$103.49	$103.50	$103.50
7 purchase totals =	$1,142.71		$1,247.7167	$1,247.72	$1,247.80	$1,247.70