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	$64.66	5.560%	$68.2551	$68.26	$68.25	$68.30
Purchase #2	$29.25	7.613%	$31.4768	$31.48	$31.50	$31.50
Purchase #3	$245.60	5.295%	$258.6045	$258.60	$258.60	$258.60
Purchase #4	$130.89	10.275%	$144.3389	$144.34	$144.35	$144.30
Purchase #5	$202.78	6.238%	$215.4294	$215.43	$215.45	$215.40
Purchase #6	$134.69	12.644%	$151.7202	$151.72	$151.70	$151.70
Purchase #7	$23.82	6.746%	$25.4269	$25.43	$25.45	$25.40
7 purchase totals =	$831.69		$895.2518	$895.26	$895.30	$895.20