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	$244.35	12.429%	$274.7203	$274.72	$274.70	$274.70
Purchase #2	$28.25	11.540%	$31.5101	$31.51	$31.50	$31.50
Purchase #3	$224.39	13.244%	$254.1082	$254.11	$254.10	$254.10
Purchase #4	$94.58	6.328%	$100.565	$100.57	$100.55	$100.60
Purchase #5	$168.97	10.820%	$187.2526	$187.25	$187.25	$187.30
Purchase #6	$153.35	11.490%	$170.9699	$170.97	$170.95	$171.00
Purchase #7	$24.38	6.133%	$25.8752	$25.88	$25.90	$25.90
7 purchase totals =	$938.27		$1,045.0013	$1,045.01	$1,044.95	$1,045.10