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	$187.51	10.809%	$207.778	$207.78	$207.80	$207.80
Purchase #2	$158.92	8.376%	$172.2311	$172.23	$172.25	$172.20
Purchase #3	$147.55	13.778%	$167.8794	$167.88	$167.90	$167.90
Purchase #4	$150.31	6.613%	$160.25	$160.25	$160.25	$160.30
Purchase #5	$87.78	12.643%	$98.878	$98.88	$98.90	$98.90
Purchase #6	$132.75	7.412%	$142.5894	$142.59	$142.60	$142.60
Purchase #7	$212.69	7.819%	$229.3202	$229.32	$229.30	$229.30
7 purchase totals =	$1,077.51		$1,178.9261	$1,178.93	$1,179.00	$1,179.00