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	$140.86	3.145%	$145.29	$145.29	$145.30	$145.30
Purchase #2	$99.63	8.719%	$108.3167	$108.32	$108.30	$108.30
Purchase #3	$36.52	9.172%	$39.8696	$39.87	$39.85	$39.90
Purchase #4	$243.68	10.748%	$269.8707	$269.87	$269.85	$269.90
Purchase #5	$115.64	6.477%	$123.13	$123.13	$123.15	$123.10
Purchase #6	$98.77	10.626%	$109.2653	$109.27	$109.25	$109.30
Purchase #7	$235.32	13.268%	$266.5423	$266.54	$266.55	$266.50
7 purchase totals =	$970.42		$1,062.2846	$1,062.29	$1,062.25	$1,062.30