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	$212.86	8.461%	$230.8701	$230.87	$230.85	$230.90
Purchase #2	$183.25	9.654%	$200.941	$200.94	$200.95	$200.90
Purchase #3	$138.55	6.842%	$148.0296	$148.03	$148.05	$148.00
Purchase #4	$120.49	3.218%	$124.3674	$124.37	$124.35	$124.40
Purchase #5	$30.27	6.618%	$32.2733	$32.27	$32.25	$32.30
Purchase #6	$83.82	7.751%	$90.3169	$90.32	$90.30	$90.30
Purchase #7	$241.91	3.455%	$250.268	$250.27	$250.25	$250.30
7 purchase totals =	$1,011.15		$1,077.0663	$1,077.07	$1,077.00	$1,077.10