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	$179.28	4.832%	$187.9428	$187.94	$187.95	$187.90
Purchase #2	$35.33	10.488%	$39.0354	$39.04	$39.05	$39.00
Purchase #3	$39.87	7.391%	$42.8168	$42.82	$42.80	$42.80
Purchase #4	$250.85	3.474%	$259.5645	$259.56	$259.55	$259.60
Purchase #5	$148.39	6.718%	$158.3588	$158.36	$158.35	$158.40
Purchase #6	$87.25	3.457%	$90.2662	$90.27	$90.25	$90.30
Purchase #7	$16.52	5.719%	$17.4648	$17.46	$17.45	$17.50
7 purchase totals =	$757.49		$795.4493	$795.45	$795.40	$795.50