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	$89.92	8.367%	$97.4436	$97.44	$97.45	$97.40
Purchase #2	$72.83	10.839%	$80.724	$80.72	$80.70	$80.70
Purchase #3	$235.40	8.193%	$254.6863	$254.69	$254.70	$254.70
Purchase #4	$145.35	6.354%	$154.5855	$154.59	$154.60	$154.60
Purchase #5	$51.94	4.696%	$54.3791	$54.38	$54.40	$54.40
Purchase #6	$145.32	7.738%	$156.5649	$156.56	$156.55	$156.60
Purchase #7	$24.59	13.276%	$27.8546	$27.85	$27.85	$27.90
7 purchase totals =	$765.35		$826.2380	$826.23	$826.25	$826.30