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	$40.72	12.705%	$45.8935	$45.89	$45.90	$45.90
Purchase #2	$114.83	13.169%	$129.952	$129.95	$129.95	$130.00
Purchase #3	$66.67	10.463%	$73.6457	$73.65	$73.65	$73.60
Purchase #4	$202.26	7.713%	$217.8603	$217.86	$217.85	$217.90
Purchase #5	$19.25	13.857%	$21.9175	$21.92	$21.90	$21.90
Purchase #6	$86.32	6.201%	$91.6727	$91.67	$91.65	$91.70
Purchase #7	$112.64	12.853%	$127.1176	$127.12	$127.10	$127.10
7 purchase totals =	$642.69		$708.0593	$708.06	$708.00	$708.10