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	$116.76	3.588%	$120.9493	$120.95	$120.95	$120.90
Purchase #2	$77.86	6.317%	$82.7784	$82.78	$82.80	$82.80
Purchase #3	$154.59	13.308%	$175.1628	$175.16	$175.15	$175.20
Purchase #4	$41.28	8.685%	$44.8652	$44.87	$44.85	$44.90
Purchase #5	$92.56	13.819%	$105.3509	$105.35	$105.35	$105.40
Purchase #6	$10.38	13.286%	$11.7591	$11.76	$11.75	$11.80
Purchase #7	$140.89	4.215%	$146.8285	$146.83	$146.85	$146.80
7 purchase totals =	$634.32		$687.6942	$687.70	$687.70	$687.80